Hello, friend!
There may be two problems with this scenario:
1. The ACS reports only HTTP 200 OK to the ONT but does not respond to the ONT with the information response message.
2. During ont report, the ACS does not issue a work order to set the user name and password for the connection. As a result, the user name and password for connecting to the ONT are empty, and the ACS fails to connect to the ONT.
This problem needs to be checked on the ACS side.

Thanks!