Why won’t my Mac add my printer?
If you can’t add the printer because it doesn’t appear in the list of available printers, it may be turned off, or your Mac may be on a different network now. If the printer was shared by another user, the user may have stopped sharing it, or the user’s Mac may be offline.
Why can’t My computer find my HP printer?
Restart your computer and then go back to System preferences – Printers and scanners. Click the “Add button” (+). Find, and then select the name of your printer from the printer list, and then click “Add” to add your printer. Click “Print Using…” or “Use”, and then select Secure AirPrint or AirPrint.