I ran into this today. Open a browser (the same one Rack opens when you go to browse the library) and log into your VCV account, then open Rack and run the update.
This page gives me the following error:
{“error”:“Token was not given or is invalid”}
reading above in the thread, I realized that I use Firefox/Brave/Vivaldi but am only logged in on one of the browsers. The link opens in Edge on Win10 (and Safari on Mac) because I leave them as the default browser. Logging in on Edge fixed it…
Oh geez - I feel silly now. Yes, I also had the issue with the invalid token, but after logging into the correct browser, I didn’t realize it was downloading an installer exe. I assumed it was like the module updates. Doh