Just purchased BIAB Pro (2023 plugin v. 5.1.25). Everything installed correctly. The standalone version works correctly. The vsti was installed in the correct folder. I opened Reaper, inserted vsti on a new track, selected BIAB vsti. It opened up but said it was a "trial version". I had to activate with my serial number which seemed weird to me but it seemed to work. I selected file, open, recent BIAB song. It said "loading song", then "shutting down BIAB song engine", then "retrieving active styles" then nothing opened. I switched to trying a new song in the plug-in. Opened the style picker, picked a file (seemed to work correctly) but it did not load into the plug-in.
Any suggestions????
Thanks!!

In the plugin, open the Style Picker and click the Rebuild button at the bottom. Do a Fast Rebuild and see if that helps.