Security Warning when printing from iPad and iPhone but not Mac

Just today I started getting a security warning that my printer had changed (it had not) or my connection was ‘untrustworthy’ when I tried to print from my iPad and my iPhone. This doesn’t happen with my Mac which is wired into my Xfinity router. Xfinity says it’s not their problem. The printer is an HP 4100. My neighbors say they get this message ‘all the time’. The neighbors, like me, print from an Apple product to an HP printer. Their printers are different models than mine as are their Apple products. I’ve reset everything and still get the message.

Probably unrelated, I updated my Apple Watch and iPhone (watch app) today.

Is this message an Apple generated message? How do I make the message stop appearing?