Rebooting/restarting your router/wifi sometimes convinces them to reconnect.

Yeah, they should have a troubleshooting guide. Bit tricky, there can be a few reasons for a missing neutral - power through fixture wiring is quite common, no pun intended ;), loose wires another....

If it's not a loose wire then it's power through fixture wiring and the HS200 won't work there. There's enough juice to power the switch until you send power to the light. Then it loses power, resets...

If you have 4 wires in one bundle (one will be red) and another switch this is probably a 3-way switch installation which is not supported by the HS200. You need to use the HS210 or do something...

If you have a spare android device that can be dedicated to it you could run my app AutomationManager as a hub/server for the TP Link devices. It can log power use to google sheets that you could...

Power cycle the smart plug? Unplug it, wait a few seconds, plug it back in. To power cycle the camera you'd plug it into the smart plug and use kasa to turn it off, wait a few seconds, then turn it...