Thanks Larsi. I've watched a few YouTube videos but may not have seen this one

Edit - Yes, I've seen this one and this is the video that told me that my printer wasn't connected to my home network. I just can't reach the part where I should have the option to change networks because it's not prompted by the hp app.

Thanks for trying to help.

So back to the Apple app store. Is there a hp printer app for ios 9 or higher?

Most printers will have the option to set up wifi somewhere in their own software. Try going into the printers menu and see what you see there.