HA installation suddenly today has the zigbee2mqtt suddenly won't now start and I can't access any add on logs. I get a 500 server error. Seems to show logs initially after a reboot but then stops working

Configuration Zigbee
2

Did you update to zigbee2MQTT version 2.0.2 without reading the release notes?

There are a few changes you have to make.

See: Zigbee2MQTT 2.0.0 breaking changes · Koenkk/zigbee2mqtt · Discussion #24198 · GitHub

And a summary here: Zigbee2MQtt not working after update to 2.0.0 - #8 by tom_l