Restart the affected computer usually fixed mine. Reattached cable too if you are using parallel.

Sometimes restart the printer + print server to clear the memory helps too if multiple client is accessing the printer via print server.

Your printer connected to a switch like device instead of PC? Is your print server in good condition? Mine had a bad capacitor before and my colleague went out to buy a replacement which dont work that well. In the end, I opened up the print server and replace the bad capacitor. It has not had a problem until now. We have been using it for more than 15 years.