Sorry, the database connection information used in the specified installation of SMF cannot access the installation of phpBB3. This may either mean that the installation doesn't exist, or that the MySQL account used does not have permissions to access it.
The error MySQL gave was: SELECT command denied to user 'zenith_smf120'@'localhost' for table 'pokechamps_users'
What the?
TheZenith,
Most likely it is a conflict with the DB user and/or password within the two DB's.
Be sure and check the Settings.php in the SMF and your config.php in the phpBB.
Be sure that the info is correct.
You could use the same user and password for both, making it much easier to control.
I hope this helps,
tronyx
In addition, if you have two different databases and databaseusers assigned to each install, make sure they have access to both databases.