I've used Nox App Player many times and the only error message that I've encountered was the one where I had to sign into an account to download an application, even if I already was logged on. I suggest logging on Gmail one time on the browser installed on your PC, then switch back to Nox App and remove the account from Settings > Accounts > Your Account > Remove account.
Reboot your PC and add the account again and it should work properly this time.
