iCloud is not accepting my Apple ID
There are several reasons why you can't setup a new AppleID with a previously used email such as it's used as an emergency contact / backup account for another AppleID and verified or it's already the primary account.

No matter what the case, your best bet is to follow precisely the steps at:


https://iforgot.apple.com/password/verify/appleid


There is a link below if you can't unlock the AppleID you think you had titled "Forgot AppleID" at the end of that online tool, there will be a link to contact Apple Support - they are truly the ones best suited to help you with your specific details. They can look up purchases, talk with you to determine your AppleID and help unlock if needed.