I’ve been using Cantabile Lite for a year now. Recently I’ve re-install it with the latest version and it worked fine when I run for the first time - it sees all VST plugins. Great.
Exit, run again - NO plugins available. At all.
Re-install. Run. All plugins are visible.
Exit. Run again - no plugins available.
Welcome to the forum. This one has me stumped. Cantabile has the ability to be launched referencing different configuration files. Perhaps somehow you’re running it the second time from a shortcut that is referencing an empty setup.
Try when you launch it the second time to go into C:\Program Files\Topten Software\Cantabile 3.0 and run the executable from there.