I believe this is either something wrong with the iMac or something on the network I've yet to discover. I'll give as much detail as I know.
A friend has a rather simple network at home, a Comcast modem/router combo, DHCP and router functions come from this. An Airport Extrememe plugged into it and set to bridge mode, this is used for WiFi, which every device in the house is on, nothing is through ethernet and nothing is connected to the WiFi from the Comcast modem/router.
They have an iMac, a Windows laptop, an Epson printer and an HP printer. The iMac is supposed to print to the Espon printer.
The iMac can see the printer and add it through the Bonjour service just fine, it will occasionally even be able to print to it. However lately it stopped being able to print to it, it can ping it, navigate to the web interface, if you remove it from printers you can see it there to add it back. The printer is setup on the same WiFi network and we have attempted troubleshooting both with the printer on DHCP as well as with a static IP (Although I don't know enough about Bonjour to know if that is even a factor - I believe not).
When you try and print it says "Look for printer" this message never goes away. He got fed up and tossed the printer assuming it was broken, went out and bought the exact same model again, same exact issues.
No other devices in the house have issues, they can communicate just fine so I don't think there is an IP conflict or some second router hidden somewhere handing out IP addresses, but I haven't ruled that out - they don't know much about there home setup, they didn't even know they had an Airport Extreme, I found it under the bed plugged in after I noticed the SSID on their modem/router was different from what they were connecting to.
I made sure his OS was up to date (Currently 10.12.12 as of today) on the iMac as well. The Windows laptop doesn't ever use the Epson printer, but I could test using it if it would assist in troubleshooting.