Hi All,
Thought I'd fill you in on something I learned about this 3100 software patch in 2021...
So, like everyone else, in 2017, the PVR ability stopped on my Pace 3100, but I can still play back and feed 2 still has a signal.  
I have never used a paired card with this one, just a really old one a friend gave me years back, so annoyingly, I've had to put up being caught on the wrong side of the "HD swap" (i.e, ITV2 HD is 118 which I can't get so I have to go to 818 for example).
 
Anyway, since 2017 I have not lost the ability to play recordings back, and still have this ability to this day, it still lets me set recordings but it fails when it goes to. Which is interesting.
But here is my discovery, so the other day, I put an active card in this unit one with a genuine paid sub on it and set something to record, normally, this would fail if the card was not paired to this box but this not only set but it recorded the programme! - and it plays back! (I recorded from BBC One to be clear).
When I swapped the cards back, i lost the ability to record again but the programme I recorded here in 2021 will play, anytime I want it to!
 
Unlike a YouTube video of this patch I saw once, I still need a card in the box to play back, it seems to me that there is more than 1 version of this patch out there, I have one that requires a card present but others have one that works with no card, so here is my theory to get some brains thinking on this one...
 
What actually did change in 2017? I thought the software updated over-air wiping the patch out, but clearly something with the cards have changed, to test this out, I got hold of another friends old card and put that in (just to see if that would record as the card I use in the 3100 normally was present and powered on at the time the recording all stopped) and this other non-sub card actually refused to play recordings back, so behaved as Sky would have intended...
 
My post is inconclusive here, that is all I know, but I thought I'd share it because it appears to me that this patch could be customised further in 2021 to allow recording and timeshifting once more!
 
NOTE: I am a newbie to this and admit I didn't flash the box myself, I got it from ebay, a link I found on this forum years ago!