I suddenly have been unable to receive Gmail emails through Thunderbird. I have tried all the recommended fixes but cannot get anything to work. Using the "Cannot receive messages" instructions I open Tools, then Account settings and a box opens which will only allow me to add email accounts. There seems to be no way I can proceed to Server settings. When trying to get Gmail emails, the following messages appear: Sending of password for user pgzadow@gmail.com did not succeed. Mail server pop.gmail.com responded: Username and password not accepted. Sending of password for user pgzadow@gmail.com did not succeed. Mail server pop.gmail.com responded: Application-specific password required: https://support.google.com/accounts/answer/185833 Whatever I do these messages always appear and I am making no progress. Please help.