How to resolve 'Cannot verify username or password' error for Mail on iMac M3 with macOS Sequoia 15.6.1?

I am unable to get the Mail function to accept the credentials for a user on my iMac M3 using Sequoia 15.6.1. It had been working until they got locked out of their account on the web, which is now fixed. I tried to use the original Mail account but that didn't work, so I created a new account and used the new credentials. It continues to say "Cannot verify username or password, even though they are correct.

Any help would be greatly appreciated.

I have attached an image with the information for the account.

Thanks

[Re-Titled by Moderator]

Original Title: Mail problem on iMac