You had the opportunity to use the MBG, but obviously chose not to do so.

There is no going around in circles at all... just opening a request within the allotted time frame, and escalating said request also within the allotted time frame. There's no requirement to communicate with the seller at all outside of the request.

Unfortunately for you, simply allowing the request to time out (as it appears you have done) means you lose, as eBay assume you and the seller have reached a satisfactory resolution. Let's face it, if you weren't happy, you'd follow the steps to get your money back, right?

Sorry to be the bearer of bad news, but once a request is closed it can't be reopened... so the availability of the MBG for this transaction has now expired. 

Had you followed the appropriate procedure and asked eBay to step in, the request would in all likelihood have been found in your favour. You'd have got your money back and if the seller hadn't provided a return label, there would have been no need to return the faulty product.