Hi friend.
Do you mean that the ONTs connected to an OLT cannot access each other?
To solve this problem, you can configure the same service VLAN for the ONUs connected to the OLT and bind the ONUs to a VLAN profile. Layer 2 communication can be enabled in the configuration file.
If you have any questions about FTTH configuration, the links below may help you learn more.
FTTH Configuration
Thanks.