A security breach may require a password change for the existing user. However, after changing the password, it is not possible to synchronize a replica. In some cases, the following message is returned:
Error: "Check your username and password and be sure the maximum number of connections to the database have not exceeded"
The replica remembers the old connection string. With the password reset, the replica is unable to connect to the geodatabase, which leads to the synchronization failure.
Manually navigate to the new database connection on the Synchronize wizard.
For more information on synchronizing replicas, refer to: Synchronizing connected replicas.