Have you had any joy with this? I’m on hold to them now, had the same issue since yesterday. You’re the only other reference to code S104 on the whole internet!! I’m stuck at 83%
After an hour I spoke to someone. He said he didn’t have that code on his system and booked an engineer for Wednesday.
There's a workaround for this. Switch your box off, unplug the white cable from the back, then switch back on again. Wait for it to get stuck on 16%, then reconnect the cable.
Out of interest, are you in Liverpool?
Randomly, by the time the engineer arrived it had started working. It had been off for 3 days, stuck no higher or lower than 83% all the time.
Not Liverpool, Chorley.