Isn't it a bit unlikely to get that perfect storm of someone on OCUK actually also needing to perform an ebay return at the same time as you need confirmation if it works or not. Its not like me or anyone else is going to start a return of something we bought and that arrived ok and as described just to check it works (or not)
I suspect ebay Help/Webchat etc might be the better place to ask
ps first try another browser to rule out whatever browser you normally use as possibly not being compatible with whatever the returns form/page is trying to do when it loops back