Thanks, it was Natasha Maxine who dealt with my email in 2016. The original account was lands-afar.itch.io, which was set up using my primary email which is also my main PayPal address. She had deleted that account, as when I try to reset the password for the email registered with it it says email not found. But I can't add the email to my additional emails (which is required to set up PayPal) as it says email already in use with another user.
Seems like that the account was made dormant and inaccessible, but the email for it is still seen by the system. If the account could be reactivated again, then I could change the email registered with it which I think would be the simplest solution. Thanks.