I was upgrading to 1.16.0 today on a Windows 10 machine (from 1.14.4) and got this error right after. Have never seen this one before. I did NOT exit the Tailscale app or stop the Tailscaled service prior to upgrading, but I have never done this for past upgrades.
Fix was easy enough. I had to stop the Tailscaled service, make sure nothing Tailscale* was showing up in Task Manager, then I just reinstalled.
Just throwing this out there for awareness. Will test on another Windows machine later today.
Tailscale backend error:
GotNotify: Version mismatch! frontend=“1.14.4-t682d4a31e-g910f31d07” backend=“1.16.0-t86bcf6a96-gf787a582e”