Try the given methods to fix the HP Printer Offline issue in Windows 10:
To open Devices, type "devices" into the search box or ask Cortana to do so. Select scanners & printers. Make sure that "Let Windows manage my default printer" is unchecked. If necessary, click the box to unselect it. Choose your printer from the drop-down menu. Select the version of your printer that is showing an idle or online status if your printer is listed numerous times. Press Manage. Set as default by clicking the button.