Welcome, Omlata!
The DBTPMLIB is a libname statement that's automatically generated based on your data mart library plus your business context settings. If you're seeing "not assigned" errors, that's just a symptom of the real problem. Earlier on in your logs you'll probably find an error where that libname statement was attempted that explains why it failed, which is the root cause of your problem.
If you can get to that error, it will certainly aid in the speed of resolution, but you're of course always welcome to send your CI Core log file in to technical support to get their assistance in finding it and providing suggested solutions to your specific case!