I have a desktop PC plus an XBOX one. Both signed into my MS account. Until today (well that's when I first noticed) both the PC and the XBOX one are listed under 'My Devices' when I login to the account.microsoft.com

However now the XBOX one listing is missing. And it won't seem to re-appear. I tried checking for other devices and nothing picks up. I logged out of MS account and then back in on the XBOX one and still no joy. Any ideas why this might be occurring? I ended up manually registering the device and adding the serial number. Which after a while made it appear under 'my devices'. Although it still doesn't appear under 'Devices with apps and games that you downloaded from the Store', I can only see my PC still.

this is strange behaviour!