ceasley on "[Plugin: WP w3all phpBB] "Requested User Not Found" when trying to assign permissions"

Ok, i expect WP db dump, instead you've send me the phpBB db.
I only can presume so from results ...
i see, for example, user Angelicca exist with ID as assigned group ID 5, admin group. This user has not been added with WP transfer as the transfer only assign group ID 2 (normal user also if it is admin on WP).
I presume that you have send me a phpBB fresh install dump, where you have only perform users transfer.

Now so, i presume you have a not fresh install.
To fix your Angelicca user, by the way, as you mention on email, if finally this is what you want achieve, you need to just run this query with your phpmyadmin (SQL tab), when into your phpBB db:
INSERT INTO 'phpbb_acl_users'('user_id','forum_id','auth_option_id','auth_role_id','auth_setting') VALUES ('54','0','0','5','0')
this will fix user Angelicca, in a dump like the one you have send me.