TT uses the same database(s) as the HUD is configured to use - see the
Tutorial: Configuring HUD Options for how to configure that - make sure that the correct database is enabled.
Make sure that you're searching for the correct limits (i.e. you're selecting the big blind amount, not the 100x buy-in that some sites quote - if you're playing $1 big blind, search $1 NL, for instance).
I assume you're searching for limits which you have data on, but you might want to turn off 'stats from current limit only' (click Configure in TableTracker).
If your search is returning a lot of tables, and you have a lot of data, it can take a little while for the whole table to populate with stats, so give it a minute and see if it updates.
Also make sure that the cache is up to date for all databases used by the HUD/TT - it will have a significant effect on performance if the cache is out of date. You can see the cache status in the status bar at the bottom of PT3. Try running Database > Housekeeping for all databases used.