Hello, resurrecting this post as I am facing a similar problem.
We had a very old UBBThreads forum (6.2.3). I successfully got the forum to 6.5.5 and it looks all good.
I am struggling with importing 6.5.5 to 7.x using the Import Script Version 1.1 provided in the members portal.
Importing to the following versions has failed: 7.0.0, 7.1.0, 7.2.0, 7.3.0, 7.7.4.
7.0.0: Import fails, missing required file 'libs/html.inc.php' (threads_import.php, line 40)
7.1.0: Import fails, missing required file 'libs/html.inc.php'
7.2.0: Import fails, missing required file 'libs/html.inc.php'
7.3.0: Import was successful, and able to log in. But all posts have username = Anonymous. My guess is the username logic (threads_import.php, lines 1059-1067) is not compatible with 7.3.0.
7.7.4: Usernames failed to carry over, unable to log in.
Since the import takes a long time to run, I thought I would ask before trying any other versions.
Is there a known UBBThreads version that is compatible with the UBB.threads Import Script Version 1.1 (March 03, 2007) ?