What is the problem?
The octoprint instance is no longer accessible on my Raspberry Pi 3B+ via hostname after a print starts, I always have to use an IP address if I want to access the instance. I have another instance on a Raspberry Pi Zero W that has worked perfectly since day 1. Typically I pull the power to restart it and then I can access the octoprint instance via hostname.
What did you already try to solve it?
Swapping out power supplies. I also put a USB voltage/amp meter to make sure at least 5V was being supplied to the Pi. I've tried a dedicated power supply and a phone charger, both capable of 2.5A with no success. Pinging the device via hostname does not result in a reply, pinging the device via IP does result in a reply.
Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware,
serial.log or output on terminal tab, ...)
OctoPrint 1.3.11 running on OctoPi 0.16.0