Server & session up but connection not responding

I'm using the same configuration for NICE-DCV in 2 different regions: us-east-1 and us-east-2. I've been working with the former for a longt time but the latter is giving me trouble for some reason that I cannot figure out. The server is up and running:

? dcvserver.service - NICE DCV server daemon
     Loaded: loaded (/lib/systemd/system/dcvserver.service; disabled; vendor preset: enabled)
     Active: active (running) since Fri 2024-01-05 14:00:44 UTC; 13min ago
   Main PID: 870 (dcvserver)
      Tasks: 7 (limit: 9309)
     Memory: 30.6M
        CPU: 2.914s
     CGroup: /system.slice/dcvserver.service
             ??870 /bin/bash /usr/bin/dcvserver -d --service
             ??950 /usr/lib/aarch64-linux-gnu/dcv/dcvserver --service

Jan 05 14:00:34 ip-172-31-15-129 systemd[1]: Starting NICE DCV server daemon...
Jan 05 14:00:35 ip-172-31-15-129 modprobe[869]: modprobe: WARNING: Module v4l2loopback not found in directory /lib/modules/6.2.0-1017-aws
Jan 05 14:00:44 ip-172-31-15-129 systemd[1]: Started NICE DCV server daemon.

and the session is also OK. However, and when I try to connect from the web browser (have tried different ones), it keeps signaling 'connecting' without actually connecting until I get a "non responding error."
The O/S is Ubuntu22.04. It doesn't seem that I can upload the logs but the last lines of the server log read:

...
2024-01-05 14:05:51,498833 [   950:950   ] INFO  ws-transport - Setting message reception timeout to 30 seconds
2024-01-05 14:05:51,568859 [   950:950   ] INFO  channel - Channel dcv::display (10, 0xaaab2010cf80) of connection 6 successfully established with client 73.214.252.31:61452
2024-01-05 14:05:51,569778 [   950:950   ] INFO  backend-handler - Received channel backend connection 'display' request from agent (PID: 1376 - user: ubuntu) to connection 6 of session 'model-user'
2024-01-05 14:05:51,569792 [   950:950   ] INFO  backend-handler - Authorized connection 'display' from channel backend 'PID: 1376 - user: ubuntu' to connection 6 of session 'model-user'
2024-01-05 14:05:51,570071 [   950:950   ] INFO  agent-controller - Established channel backend connection 'display' to connection 6 of session 'model-user' with transport 0xaaab20112d30
2024-01-05 14:05:51,570089 [   950:950   ] INFO  display - Channel proxy established, splicing the transports
2024-01-05 14:05:51,570106 [   950:950   ] INFO  agent-controller - Agent connection 'handled'
2024-01-05 14:06:00,051295 [   950:950   ] WARN  main-channel - Cannot ping channel 73.214.252.31:61443 as previously RTT measure is still in progress for session 'model-user' (status: 2)
2024-01-05 14:06:05,051223 [   950:950   ] WARN  main-channel - Cannot ping channel 73.214.252.31:61443 as previously RTT measure is still in progress for session 'model-user' (status: 2)
2024-01-05 14:06:10,051169 [   950:950   ] WARN  main-channel - Cannot ping channel 73.214.252.31:61443 as previously RTT measure is still in progress for session 'model-user' (status: 2)
2024-01-05 14:06:15,051117 [   950:950   ] WARN  main-channel - Cannot ping channel 73.214.252.31:61443 as previously RTT measure is still in progress for session 'model-user' (status: 2)
2024-01-05 14:06:20,051244 [   950:950   ] WARN  main-channel - Cannot ping channel 73.214.252.31:61443 as previously RTT measure is still in progress for session 'model-user' (status: 2)
2024-01-05 14:06:25,051055 [   950:950   ] WARN  main-channel - Cannot ping channel 73.214.252.31:61443 as previously RTT measure is still in progress for session 'model-user' (status: 2)
2024-01-05 14:06:30,051115 [   950:950   ] WARN  main-channel - Cannot ping channel 73.214.252.31:61443 as previously RTT measure is still in progress for session 'model-user' (status: 2)
2024-01-05 14:06:35,051114 [   950:950   ] WARN  main-channel - Still cannot ping channel 73.214.252.31:61443 after 35 seconds as previously RTT measure is still in progress for session 'model-user' (status: 2)
2024-01-05 14:06:35,051143 [   950:950   ] INFO  main-channel - Closing connection after ping error
2024-01-05 14:06:35,130100 [   950:950   ] INFO  channel - Channel dcv::main (6, 0xaaab200a9600) of connection 6 disconnected from client 73.214.252.31:61443 for reason transport-error
2024-01-05 14:06:35,130170 [   950:950   ] INFO  channel - Failed to receive message (connection-id=6, channel='dcv::main', channel-id=6, client='73.214.252.31:61443'): Operation was cancelled
2024-01-05 14:06:35,210784 [   950:950   ] INFO  channel - Channel dcv::audio (8, 0xaaab200dc0d0) of connection 6 disconnected from client 73.214.252.31:61450 for reason normal
2024-01-05 14:06:35,210875 [   950:950   ] INFO  channel - Transport splice interrupted due to error (connection-id=6, channel='dcv::audio', channel-id=8, client='73.214.252.31:61450'): Operation was cancelled
2024-01-05 14:06:35,211055 [   950:950   ] INFO  channel - Channel dcv::input (9, 0xaaab200dea30) of connection 6 disconnected from client 73.214.252.31:61451 for reason normal
2024-01-05 14:06:35,211098 [   950:950   ] INFO  channel - Failed to read message (connection-id=6, channel='dcv::input', channel-id=9, client='73.214.252.31:61451'): Operation was cancelled
2024-01-05 14:06:35,211240 [   950:950   ] INFO  channel - Channel dcv::display (10, 0xaaab2010cf80) of connection 6 disconnected from client 73.214.252.31:61452 for reason normal
2024-01-05 14:06:35,211325 [   950:950   ] INFO  channel - Transport splice interrupted due to error (connection-id=6, channel='dcv::display', channel-id=10, client='73.214.252.31:61452'): Operation was cancelled
2024-01-05 14:06:35,211440 [   950:950   ] INFO  connection - Disconnected last channel (dcv::clipboard) for connection 6, closing connection
2024-01-05 14:06:35,211452 [   950:950   ] INFO  agent-controller - Removing all redirected printers for connection id '6'
2024-01-05 14:06:35,211459 [   950:950   ] INFO  Cups:cups-manager - Received remove printers request for connection id '6' and session index: '1'
2024-01-05 14:06:35,211473 [   950:985   ] INFO  Cups:cups-manager - Worker: Removing virtual printers for connection ID '6' and session index: '1'
2024-01-05 14:06:35,215426 [   950:950   ] INFO  agent-controller - Notify client connection id '6' (status: 'CLOSED', tag: '', current_connections: '0') from server to agent 'full' of session 'model-user'
2024-01-05 14:06:35,215484 [   950:950   ] INFO  session-manager - Client 6 (user: ubuntu) disconnected from session with ID model-user with reason no-error
2024-01-05 14:06:35,215496 [   950:950   ] INFO  session - Last connection closed and session unlocked, locking OS desktop session
2024-01-05 14:06:35,215519 [   950:950   ] INFO  clipboard-dispatcher - Stop clipboard monitoring
2024-01-05 14:06:35,215528 [   950:950   ] INFO  channel - Channel dcv::clipboard (7, 0xaaab200f8f80) of connection 6 disconnected from client 73.214.252.31:61447 for reason normal
2024-01-05 14:06:35,215588 [   950:950   ] INFO  channel - Failed to read message (connection-id=6, channel='dcv::clipboard', channel-id=7, client='73.214.252.31:61447'): Operation was cancelled
2024-01-05 14:06:46,427739 [   950:950   ] INFO  session-manager - There are 1 active sessions
2024-01-05 14:06:46,427774 [   950:950   ] INFO  session - There are 0 active connections on session model-user
2024-01-05 14:07:46,428415 [   950:950   ] INFO  session-manager - There are 1 active sessions
2024-01-05 14:07:46,428464 [   950:950   ] INFO  session - There are 0 active connections on session model-user
2024-01-05 14:08:46,428742 [   950:950   ] INFO  session-manager - There are 1 active sessions
2024-01-05 14:08:46,428785 [   950:950   ] INFO  session - There are 0 active connections on session model-user

Thanks.