cannot connect from web application to oracle rds from ISP

Hello, I am new to AWS and have setup an oracle (rds) instance which is working fine for my web application when I test with my local development machine. When I test from my ISP, the connection to oracle fails with a connection timeout. I asked the ISP to ping my oracle server and they said it was failing and I might need to whitelist outbound IPs on AWS. Can someone here please advise on how I can do this? Or, is there something else I need to do?
My connection is done through a web.config file as…
<add name="ConnectionOracle" providerName="Oracle.ManagedDataAccess.Client" connectionString="Data Source=orcl.crkjumjl6ubz.us-east-2.rds.amazonaws.com:1521/ORCL;User Id=SchemaTrack_master;Password=mypassword;persist security info=false;Connection Timeout=120;" />
The timeout error I get is…
System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 3.18.122.118:1521

Thanks very much.

Edited by: gunderj on Mar 27, 2019 9:01 AM