To get your HP printer back online, follow these steps:

1. **Check the physical connections**:
– For USB printers, ensure the cable is securely plugged into both the printer and computer.
– For wireless printers, confirm the printer is connected to your Wi-Fi network properly[1].

2. **Restart devices**:
– Turn off your printer, unplug it for a few seconds, then plug it back in and power it on.
– Restart your computer and router as well. This can resolve many connectivity issues[1][4].

3. **Set the printer as default**:
– On Windows, open Control Panel > Devices and Printers.
– Right-click your HP printer and choose “Set as Default Printer.”
– On Windows 10, also uncheck “Let Windows manage my default printer,” then select and set your printer as default via Settings > Devices > Printers & Scanners[1][2].

4. **Check printer status and print queue**:
– Go to the printer settings, open the print queue, and cancel any stuck print jobs that may block printing.
– Ensure “Use Printer Offline” mode is unchecked[1][4].

5. **Update or reinstall drivers**:
– Download and install the latest HP printer drivers from the official HP website or use the HP Print and Scan Doctor tool, which can automatically diagnose and fix common problems[2][4].

6. **Run HP Print and Scan Doctor**:
– Download this free tool from HP and run it to troubleshoot connectivity and offline status issues automatically[2].

7. **Reconnect via Wi-Fi Protected Setup (WPS)** if wireless:
– Use your router’s WPS button and the printer’s WPS option to easily re-establish a secure wireless connection[2].

By following these steps—in order—you can effectively change your HP printer’s status from offline to online in most cases[1][2][4]. If problems persist, checking HP’s support resources or contacting HP support may be necessary.