The Sonoff ZBMINI-L that controls our bathroom exhaust fan goes offline once in a while. Previously I had to remove the switch to gain access to the ZBMINI-L that was behind the switch to press the reset button on the ZBMINI-L
I stumbled across this method that worked for me to get the ZBMINI-L back online without disassembling anything.
Start Zigbee pairing, then turn the switch on and off 10 times.
Some may be aware of this, but searching these forums yielded no hits.