Why is a supplier showing as inactive despite being active?

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I was wondering if anyone can help - in my list of suppliers, my most commonly used one I realised wasn't on my list, if I click 'include inactive' it comes up.  I have gone into the record and the inactive button is not clicked.  If I do click it it tells me the record cannot become inactive due to not having a 0 balance.  Any suggestions (and hope this makes sense).

Thank you