Thanks for posting on the Community Forum and sorry to hear about this.
It sounds like there is a negative amount on your balance due to the open dispute on your account. The denial message you're seeing could be for a few different reasons - our security system could be stopping your payment, or there could be a denial from your card issuer.
If you're still experiencing issues, I'd advise contacting Customer Support directly so we can help. You can find our contact details by clicking the 'Contact' option at the bottom of any page when logged in.