this doesn't work tried 100x
i can't add my sky.com email account to the macbook Air .tried 100x followed the instructions re Add Account .
Assuming you can access it via their website/webmail portal (to verify your password is correct) there are two other big possibilities:
You could have a very old account with them still using POP instead of MAPI. Check out their "Computer - Other Email Apps" section for alternative settings for POP (https://www.sky.com/help/articles/getting-started-with-sky-yahoo-mail).
You could also have an "app specific password" set up and you'll have to use their webmail portal to generate an app password (also discussed in that document).
Additionally, a very unlikely (but possible) issue would be an issue with the Mac Mail App itself with that particular email service provider, but to eliminate or confirm that you would simply download a free 3rd-party email client like Thunderbird, Hiri, etc. (just search for "macOS email client" for lots of choices) and try to set it up with the same settings you've been trying in macOS.
To explore the first two possibilities you would need to log into their website and dig deep into the Account settings to see if you have a POP vs MAPI account, or if you have an app-specific password requirement set up, or something else going on). Trying another email client at least you could check before deep diving into your account.