You have purchased a Belkin N1 F5D8051uk ver.2xxxUK which is not on the list and that is probably why it is not working. Does your Mother have the latest firmware installed as this also adds more adaptors and may be needed to get your one working. The version number is also very important as the manufacturer sometimes changes the internal chip when update the version and the WD player can only support certain chips.
can you upgrade the firmware on teh usb adapter at all?
Even if you could, that wouldn’t help.
The problem is that each actual chipset needs a different open-source driver.
The manufacturers buy 10,000 or 100,000 (or whatever number) of whatever chip is cheapest at the moment. Then, their next round of purchasing, they may buy 10,000 or 100,000 (or whatever) of a different brand of chip that is functionally identical, and put it in the same “Model” of adaptor, but with a different version/revision.
Unless the WDTV has the correct driver for whatever chip they switched to, the WDTV can’t properly use the adaptor.
That’s why the revisions matter. Just because one model worked, doesn’t guarantee future “versions” of it always will.
And, without an open-source driver for a new chip, WD kinda has their hands tied until a driver does exist for that chip.