Questioned by linkshare "Invalid account"..help me decide. lie?

Ok so I'm sooo new to this and a very long time ago I may have created a test account with linkshare using God knows what info ( couldn't be too unrelatable I suppose). Anyway I never used LS, don't think I even had access to the merchants pg yet. Now that I'm working on a public site I'm signing up to networks but Linkshare said my social was in use. Ok so then I remembered. It said the account was invalid and that I had to email them to appeal their decision... Not sure if I used my real name or alias on sign up ( which I doubt I would have put a fake name to my social unless it autofilled the name..ugh). Should I just say now I don't think I created that account?? But I don't want any investigation into a "stolen" social just bc I can't remember what I did on the form. But now I'm also uncertain about detailing my real creds via email bc if it's totally off and they say no then I'm out of luck with any other site. Would much rather do a whole new sign up if my social wasn't flagged....

Any suggestions or heads up? What are the typical reasons for this happening?

Why am I being penalized when they can see I never logged into the account since trying to sign up, never used a link or communicated with merchants.