in 10 minutes I'm going to go back to Thunderbird

if eM Client does not allow me to change my password SOON I am going to close my account…my gmail account had an attempt to hijack it this morning and google advised changing my password…which I have done but eM Client will not accept and/or recognize the change // in 10 minutes I’m going to go back to Thunderbird

You have to change the password in Gmail first and then overwrite the password in eM Client too - did you do that?