Just in case anybody else was also having the same question as me above, I've found the following article https://support.hp.com/us-en/document/c03767639 This clearly states that the printer must be connected to the internet and that a USB connection is not sufficient for Instant Ink to work.
Got mine yesterday. Registered and got 9 months free trial (300 printers per month) with additional codes
What do you mean? I ordered this and got my 7 months free instant ink?
Any recommendations on photo paper?
Be warned! You can’t get any 7 months free ink. The only code that works on any printer is the free one month, if you buy one of the higher priced printers you can claim £30 cash back.