I had a power outage recently - just 30 minutes. I have hundreds of Hue bulbs and they all came back on and once powering back on the NUC running deCONZ, all was well… except that nearly all of my 12+ dresden elektronik FLS-CT lp did NOT came back up. Phoscon shows some as working (they don’t) and some as grayed out and unavailable (true). I’ve tried removing a few and re-adding but they aren’t found.
Any thoughts?
This could be the cursed NWK security frame counter. Are they still not reachable after a while?
Usually what I’d try is to power cycle a FLS unit (keep it powered off for about 10 seconds).
Yeah, tried that. 
I even left the ones not working (most) off for 24 hours and tried again. And, again, tried removing and re-adding but that didn’t work, although I’m not sure how to “factory reset” the FLS-CT lp’s so they don’t belong to a network anymore, assuming that’s a good thing to try.
I’m up for anything!
For a full factory reset there is a on/off sequence described in Technical support
Perhaps you can try this with one FLS. You likely have already tried it but did you also hard power-cycle the ConBee/Raspbee, after power up it will bump the internal NWK counter to compensate for issues like powerloss where the latest counter wasn’t stored (other devices in the network might think there is a replay attack going on).
I will try a full factory reset and re-add on one of them.
I’m confused by the next suggestion, though. What would that process look like? Just stopping the docker container, unplugging the ConBee II, plugging it back in, and restarting the container?
Yes, that’s just what it should be.
What you can also try before the complete reset of the FLS is to start a light search in the Phoscon App and meanwhile to re-energize the FLS once.