Eprint can't find office jet 4500 connected to airport express

Hi, I have a non wireless HP Office Jet 4500 that is connected to an Apple Airport Express.

I know this model isn't compatible with airport so I have the eprint app downloaded on my apple ipad.

I have previously been able to print from this app, but lately it can't find the printer. The ipad has the latest iOS and the latest firmware on the airport.

Any help gratefully received.