I purchased the NewBlueFX Transitions 5 Ultimate package, but none of them would show up in Vegas Pro 17. I tried reinstalling both NewBlue and Vegas, but no luck. Then I contacted NewBlue support and got this answer:

Close Vegas, Delete plugin_manager_cache.bin and svfx_plugin_cache.bin from C:\Users\{user name}\AppData\Local\VEGAS Pro\{version#}, then retest.

This solved the problem, but I had to do it twice. If you're having this problem, then don't give up if deleting these files doesn't fix the problem right away. I had to delete them twice and then they showed up.