I’m having almost identical experiences with three Nanoleaf matter capable essentials bulbs. They all pair instantly in the Nanoleaf app, but beyond that is a comedy of random failures.
I was able to get all three mostly working in SmartThings but I had to replace my home router and all three went offline, never to be seen by SmartThings again. One kept working in Apple Home, the other two were ‘unreachable’. The Nanoleaf app saw all three. I finally deleted all three from every app, iCloud, and did factory resets to start from scratch.
Now I can get all three working in the Nanoleaf app, but maybe a random one into Home after enough tries. SmartThings never works, failing usually at the ‘add to iCloud’ step but sometimes when registering with SmartThings. The error is always some flavor of not being able to access the device. Been around the block on this merry go round at least 20 times.
I’ve tried every combination of which app to add to first but no luck.
I have noticed that the Nanoleaf app shows the bulbs as connected via thread or Bluetooth, bouncing back and forth randomly every few minutes. This doesn’t seem like proper behavior and I’m suspicious of the issue being related to unstable connectivity. The bulbs are about as close to the router and border devices as physically possible, so I’m hoping it’s not a distance thing. The fact they all connected before and nothing has moved makes me think this is more about poor software.