@Solla-topee 

Yes the Kasa HS 200 & HS 210 are on a Google Mesh System Model number H2D 

When everything is working normally and my Android phone is not on WiFi  I can use the Kasa app to connect to the light switches over an LTE network. However when the failure occured the Kasa app could not connect to the switches over LTE. 

Please note this is a general failure off all switches when the power outage is restored several of the switches are located within a few feet o the base router so WiFi signal is not an issue. 

I did try rebooting the mesh network after the failure was noted and this did not make a difference, the only solution that worked was to press the restart button on each switch.

Also note if you reboot the Google mesh network when the HS switches are working OK the switches come back online OK. However after the failure mode rebooting the Google NEST WiFi does not bring the switches back online. 

Note I have played with the curcuit breakers to shut off power and the HS devices boot okay. 

The symptoms I describe would seem to point to the power up boot sequence in the HS switches, when the house power is restored after an area outage I suspect that power is not restored smoothly and there is significant fluctuatrions in voltage for a short period before stabilization you probably don't see this with just flipping the curcuit breakers. 

Note the switch LED's are all white when the the problem occurs, also the Google NESTsoftware reports the Kasa switches as being on the WiFi network (but they are not contactable via IP).

Based on the way configuration of the Kasa switches work I would have to conclude the switches have some NV RAM for storing network information. I suspect that the switches may be retaining the old IP address prior to the power failure,

During the boot sequence when the whole house has power restored if there is some error condition that results in failure to obtain a new lease on an IP address I suspect that the switch is defaulting to using stored IP address. 

I'm an ex software engineer and have had to debug driver and firmware code in the past; here is a thought to comsider.

If the firmware code responds to interrupts then the power fluctations occuring when the house power outage is restored may be causing a 2nd interrupt while still processing the 1st interrupt. If the firmware coder did not account for this condition then its possible that this may the the root cause of the error .