Heya Rhodes54,
In your DAWs, look for a setting like:
"Refresh Plug-ins" - or
"Re-scan Plugins" - or
"Flush Plug-in Cache".
Also, some hosts may have a check-box in their settings like:
"Rescan Plugins on Startup"
Good luck - hope that solves things. If not keep posting.
For most people, in most circumstances, it should just work, and does. Although not quite a myth, there are always some of us who experience the times something doesn't automatically work
There are always some DAW and VST combos (some reasons below) which require some user intervention, to this day, unfortunately.
Different DAWs and hosts handle things differently, and makers of VST products can only adhere to known conditions and standards. Pianoteq has never borked anything here where other VSTs have.
Currently, VST 3 might be a cause of a few DAWs failing over as some might have been loading a VST 2 version before an update - so following from there, if said DAW has itself recently updated, and had newly coded better handling for VST3, then perhaps it's maybe just "stuck" looking for your new compatible PTQ6 inside some newly obsolete VST 2 folder.. who knows. A DAW's plugin cache will sometimes remain with incorrect pointers for the DAW, so expunging the cache is always one of the first things I do after installing any updates or new plugins.
Hopefully that's what you're also encountering, as the fix is usually a click away.
Pianoteq Studio Bundle (Pro plus all instruments) - Kawai MP11 digital piano - Yamaha HS8 monitors