Thunderbird imports from outlook, not PST files. Even then the copy of outlook must be functional and the messages loaded in outlook by default.

My guess is it may be more to do with how old the outlook instance it. 2007 has not been supported by Microsoft of most of the intervening years. While Thunderbird outlook import has had little attention over the past decade, it has had some. It is therefore possible that the importer is relying on outlook features that only appeared after 2007. It may be you need a copy of Thunderbird a little more contemporaneous with the outlook instance to succeed

HI Matt, OL is working and it is the default email client. Others have succeeded in using the Import Yool for that version of OL but there seems to be a 2GB limit to the PST size, is that still true fore the new version of TB?