I am running MAX2PLAY on a Pi Zero with a write protected SD card.
I now have the same problem. My player works OK streaming music from iTunes but all of a sudden I can’t access the web interface using either the device name or IP address. Curiously it appears on my router with the device name „localhost“ – this is DEFINITELY the Pi.
I have no access to diagnostic info as I am running on a Pi Zero embedded in a portable speaker. I have no access to the HDMI port without a complete strip down. For the same reason, flashing a new SD card will be a real pain.