Can’t add email to Outlook, IMAP wrong

Hi, I’ve several email accounts on my Outlook on my iPad. Sometimes it asks me to re-sign into an account. Never had a problem. But today it just keeps saying Invalid IMAP username/password.

Several months ago Virgin changed how I logged into my media & email account. I have to use my gmail email address.

ive tried all combinations of ntlworld or gmail addresses, along with gmail password for Virgin- no longer have password with Virgin for ntlworld address. Same invalid response.

I got so frustrated I deleted account from Outlook so I could re-enter it from scratch, another thing I’ve never had trouble with. But same Invalid message! Email comes up as normal if I go online. But need to be able to easily see ntlworld emails. Can anybody help as I’ve run out of ideas…..used Virgin chat agents, but they don’t have a clue