@Radim Smetana hope this will help you activating
Had the same problems, even after (clean) install/re-installs, regedit hacks and what have you. @Promidi put me on the right track however. Microsoft Edge Webview2 Runtime was not installed, but I didn't bother to install it as I hoped that using Edge for logging in would fix my problem, and it did:
I went to my windows settings (just search 'default browser') to change my default to Edge (windows 10). I was using Chrome until now.
Closed all browsers and bandlab apps
Opened the bandlab assistent
The login prompt page is now opened in Edge
Login works just fine!
So, for activation and login you need Edge. If you are only using Cakewalk and not the Bandlab you can just switch back your default to your favorite browser.
As far as I can tell Bandlab is using some Edge specific libraries, which I think is a no go - but if they really need this then they should make this VERY clear in the setup requirements.