No printer code ever accepted for instant inks. See screenshot.

[UKSmurfy]

 Everything set up, but no matter what, even after a factory reset, I cannot subscribe to instant inks. No instant inks account created, though payment card was accepted. Couldn't access cartridges, genuine HP installation cartridges installed and reported correctly on HP android app. No other printer on my HPConnected account. Is some firmware blocked at HP to reduce their costs, so the printer can never be subscribed? It looks like it. 

[UKSmurfy · Accepted solution]

Aha, may be I've sorted it. The DeskJet 2710 isn't on HPs list of eligible printers for Instant Inks, presumably as it's too ancient a model.

Though HP still give the impression of a business in chaos, as the printer's packaging comes plastered with stickers for Instant Inks. Why, when the DeskJet 2710 model is not eligible? And it somehow passes the running software checks on trying to sign up! How come? So may be some 2710 models are, and some aren't. Chaos! Who knows? Not the customer, who has no way of finding out, except the trial and error hard way! No-one it seems, not even HP! 

The only satisfaction is discovering in time to avoid being locked into a hit-and-miss instant inks subscription and ending up with a useless printer that can't print, when HP won't supply inks that work, and prevent anyone else's inks from being used either. What a scam wheeze!  Don't trust buggy HP software! It's just a brand name for a myriad of foreign manufacturers all it seems doing their own thing with no overall quality control!