Your processed hand history files should be in the 'processed' folder (unless you deleted it) - you can run a Manual Import of that folder to re-import them (see Auto Import tab to see where your processed folder is - this could be different if you changed it in your previous installation..).
Try running full Housekeeping and restarting PT3 - does the Details tab work now?
If not Please
enable logging, reproduce the problem and submit your PokerTracker.log file to the
Support system , and link to this thread in the reference field of the ticket so that we can investigate.