I have the same error on my Pixel 7 Pro. When I first go to Upload Web Data, it gives me an error and it takes me manually sign in, which I never have to do typically. It always remember my credentials in the past.
That initial error says "Account validation error: g3.g: Abstract classes can't be i..." and the rest is truncated from there. The error disappears really fast.
And then I attempt to sign in as being asked and I get another quick error flash on my screen, "Login error: g3.g: Abstract classes can't be instantiated! R...". And then I am back to my normal monitoring screen.
Robert