Hey There, I am Sofia Carter. If your HP printer is appearing offline on a Mac device, you need to reset the print system to fix the issue. Click the "Apple" Icon. Choose the " system preferences" option. After that, click on the " print and scan" or " print and fax" option. Right-click on the printer list and choose the option to reset the system. Choose "Reset" for confirmation. Hopefully, after this, your “HP printer offline Mac” error will be resolved. If not, get expert help.