Name/e-mail *** is not valid in phpBB - Drupal user add

I've been trying to learn more about the inner workings of this module. Here's my understanding of what's going on. If someone else knows better, please correct me.

If the user already exists in one system, there's no need to create the account in the other system. Account syncing happens automatically when a user authenticates in either system.

There is no feature to "mass sync" users in both systems. The reason for this mainly stems from how passwords are stored in both systems.

When an account is created (or a password is changed), the system encrypts the password and then stores it. Once it has been stored, there is no way to read what the original password is. So if you were to try to sync the user automatically, the other system would try to read the password but it would be garbled, and the account would essentially be invalid in the secondary system.

So how do we get the password? During the login process, or when the user edits their profile and changes their password. At that time, the code has access to the "clear-text" password which we can then encrypt differently for each system.

You might then ask "how are user profile fields synced"? Profile fields are also synced at login. In the Drupal admin pages, you specify which system is the MASTER. And when the user authenticates on either system, the profile changes are automatically pushed to the other system.

Reopen the issue if you still need help.