We have identified the problem in Paratext that has caused the issue. We are going to fix the bug, but your project that you have migrated is probably messed up. The problem is that your project contains several other .SSF files inside the project folder. During migration we were assuming there would only ever be one so the migration just takes the first one that is found. In this case, it picked the wrong one. This means that all of your project settings are wrong (the cause of your missing books). This also means it probably has the wrong ID (the cause of not being able to correctly register).
You can wait for a fix to Paratext (should come out in the next couple days) or you can remove all the other .SSF files from the project in PT7 and then do a Send/Receive in PT7.
Either way, you will have to delete everything in PT8 and start the migration over (I hope you haven’t started work on it in 8.0, yet ). You can use Project > Delete Project to do this easily.
We deeply apologize that you have had this issue.
If you have started real work on the project in 8.0, please let us know and we can work with you to preserve all the changes while getting your project straightened out. However, it will be a bit of manual work, I think.