Hold down CTRL-SHIFT and start VEGAS. You’ll be prompted with a window that has a checkbox that says “clear cache”. Check that box and continue. Please note that will also reset VEGAS back to factory defaults.
If you don’t want to reset VEGAS back to factory defaults, you can Close Vegas, Delete plugin_manager_cache.bin and svfx_plugin_cache.bin from C:\Users\{user name}\AppData\Local\VEGAS Pro\{version#}, then retest.
Keep in mind that the “App Data” folder is probably a “Hidden” folder so you will need to have Windows “Show Hidden Folders”.