Finally I had a look into the Thunderbird > Preferences > (Tools > Options for Windows users) and found that the faulty profiles had the option "Accept copies from sites" un-checked under "Privacy". As soon as I activated this option, the drop-down window "Would you like a new email address" would open with the username filled in and with buttons being responsive again.
Thanks, it correct my issue:
Finally I had a look into the Thunderbird > Preferences > (Tools > Options for Windows users) and found that the faulty profiles had the option "Accept copies from sites" un-checked under "Privacy". As soon as I activated this option, the drop-down window "Would you like a new email address" would open with the username filled in and with buttons being responsive again.
thanks