Question mark symbol on HP OfficeJet Pro 7740 printer display screen

My HP OfficeJet Pro 7740 printer has been working OK from my iMac running MacOS Mojave

version 10.14.6 - except today when no printing jobs would be completed and there is a question

mark symbol on left side of the printer display screen. Nothing that I know of has been changed.

The HP Utility on the iMac is able to connect with the printer and able to print Configuration Page.

I am able to print over WiFi from laptop computers and by email ePrint. But when I attempt to

print from a program on my iMac, nothing happens anymore. Please advise. Thanks.