Fixed: HP Laserjet Pro M428fdn Offline
Examine the power connection of the HP LaserJet Pro MFP M428FDN printer.
Make sure that the power cable of the Laserjet printer is connected its power port and electrical outlet directly.
Execute a power reset on the printer.
Make sure that the printer is connected to a router which provides an active internet connection.
Check if the Use Printer Offline option is disabled on your computer.
Run the HP Print & Scan Doctor app and try to fix the offline issue.
Reset the HP LaserJet Pro MFP M428FDN printer to its default configurations.
Reconnect your computer to the printer and check if the offline issue is solved.