Cannot print/scan via 'wireless' must use a cable to link printer/scanner with computer.

Can anyone explain?

I have a MAC BOOK AIR and an HP-printer/scanner. I print and scan vis my wireless/Internet connection. However today, the HP-printer/scanner told me it was offline and all attempts to get it back online, have failed (delete the printer/scanner then add again, rest the system via the HP app etc). The printer/scanner works only via a cable connecting it to the computer.

Can anyone tell me how to get it back online. Thanks.