DIAGNOSIS The printer's network connection is dropping, often due to an IP address conflict or the printer's sleep mode being too aggressive and not waking properly.
FIX First, assign it a static IP address on your router. This prevents your router from giving its address to another device. Find the printer's current IP on a network report (Print one from Setup > Reports > Print Network Configuration). Log into your router's admin page and reserve that IP for the printer's MAC address. Next, adjust the sleep timer. On the printer, go to Setup > Power Settings > Auto-Off and set it to a longer time or Off.
IF THAT DIDN'T WORK The firmware might be buggy. Check the current version on the network config page. Go to HP's support site, enter your model, and download the latest firmware file. Install it via the Embedded Web Server (under Settings > Update Firmware). Updates often fix stability issues.
HEADS UP If you're connecting via Wi-Fi, signal strength can be a factor. A weak signal causes drops. Consider moving the printer or router, or just use an ethernet cable—it's far more reliable for this model.