It says the the aptbtch file is locked.

I was finally able to retrieve it but this is not very convenient.
(I had already tried shutting down and rebooting. That did nothing.)

I ran a data integrity check on A/P. It returned no errors.
I ran a data integrity check on TB. It returned no errors.
I opened A/P.
I opened TB.
I retrieved data successfully.

Version:
AP 8.1A (080821)
TB 8.1A (080516)