Thanks, yes, I eventually figured that it needed a very small screwdriver in the gap between the two metal tabs as you mention. I initially tried with a bigger screwdriver which didn’t work. Though even with a new battery it’s oddly struggling to connect to the Zigbee network.
Is the little SIM card holder size button on the back for resetting? Is deleting from Zigbee2MQTT in Home Assistant and then reseting likely an option? How long should I hold it for?