Why does my printer say offline when it is clearly on?
The status reflects whether your computer can currently reach the printer, not whether the printer has power. It is genuinely a communication failure, and on a network printer the cause is nearly always addressing.
Most home printers receive their address automatically, and that address can change when the printer or router restarts. The computer still holds the old one, tries to reach it, gets nothing, and reports offline. The printer meanwhile is perfectly healthy at a different address. Assigning the printer a reserved address in your router settings prevents this permanently and is the single most effective fix.
The second cause is the print queue itself. A stuck job can wedge the queue so that everything afterwards fails and the device is marked unavailable. Clearing the queue and restarting the print service resolves it, and this is what most vendor troubleshooting tools actually do behind the scenes.
A third possibility is a duplicate printer entry. Systems often create additional entries when a device is detected in a new way, and jobs sent to the wrong entry fail silently. Removing all copies and adding the device once is cleaner than guessing which one works.
On wireless printers, verify which network the printer joined. Many homes now have separate bands or a guest network, and a printer on a different network from your computer cannot be reached even though both have working internet.
Use the printer own control panel to print a network configuration page. It reports the address and network name directly from the device, which removes the guesswork about what it thinks its situation is.