Setting up email on a different computer: configuration failure

I succeeded in the Thunderbird transfer method described in these forums when bunging it on an old Win10 laptop. When I come to try the same on a new Win11 PC however, setting up an existing email address simply fails. I get as far, in the Set Up Your Existing Email Address page as "Configuration found at email provider" but can proceed no further as I get the message "Unable to log in at server. Probably wrong configuration, username or password" The setup on my old PC is gone now, it finally gave up the ghost, I have email on the old Win10 laptop but that's far from ideal. Additional facts: it's an ntlworld email address; there's a possibility the password may be redundant (so many of these to be found when a PC is on its last legs) How do I get it onto this Win11 PC?