My sonoff ZBBridge tasmota flashed coordinator appears offline after a while even if it’s online and working.
Using zha-network-card or zigzag graphical layout, the coordinator appears “Online: false” in zha-network-card and red colored (offline) in zigzag after a couple af hour from last seen timestamp. In this seeming offline period the coordinator is indeed online and works as usual.
When last seen timestamp updates for some reason, the coordinator changes to “Online:true” or colored green again.