Simple AD not replicating

Greetings, Our Simple AD DCs don't seem to be synchronizing anymore: After joining a server to the domain only one of the two DC shows the new server record under Computers in AD Users and Computers. A new A record is only seen with that first DC, as verified via the DNS Manager. Two days later the second DC is still not synchronized - only showing the old entries. An attempt to trigger replication via Windows ADSS hangs. An attempt to run repadmin /syncall from the command prompt hangs indefinitely too. No errors in the Windows server event log. The status of the Simple AD is "Active". Is that normal? How soon Simple AD DCs are supposed to replicate? Should I resort to contacting aws technical support? Thanks.

EDIT: In addition, it appears that automatic snapshots of the Simple AD haven't been created for about two weeks now. Previously, they were created every other day or so. Also, attempts to create a manual snapshots fail.