'We are unable to process your request' - How do I contact a buyer to resolve problem?

[panthermoderns]

Hi,

I'm having a problem contacting a buyer to resolve an 'item not received' case. Each time I click 'respond' via the Resolution Center or email notifications I get the same error: 'We are unable to process your request'. I've tried several times over the last 10 days and get the same message. Now the case has been escalated and I urgently need to resolve it. Any help or ideas would be very much appreciated.

Many thanks
Tom