@ferg22 

Thanks for the replies.

The ten devices were working fine till the firmware update. Investigation revealed they were no longer getting their DHCP reserved addresses. I had made no changes to the DHCP config. The tapo devices are odd in that they had to be configured using their hardware(mac) address rather than a client identifier. Every other device I have uses client identifiers. The client identifier for these switches seems to be "P110" which, if correct, is pretty stupid.

Anyway I did all kinds of messing with the DHCP config trying to get the tapos to use their reserved addresses. This weekend I had another go and everyuthig just worked! No idea what broke it or what fixed it.

The tapo app worked fine at all times for switching the devices on and off irrespective of the DHCP assigned ip address. I wonder if it uses .local or something. However use of the reserved address is crucial for use with home assistant.

  @ferg22 Had a similar issue myself. not fully resolved yet, but I just installed a pfsense router and assigned all known devices static IPs.  1 of the P110 was fine and picked up its new IP at some point.   The others just stopped working/showing offline.  I tried doing a factory reset and could get through all the way until pairing with the wifi, at which point it would fail.

So I did a test, whilst it was pairing, I modified the MAC address on my router for the device so that it no longer had a static and straight away it picked up an IP Address from the standard DHCP pool.

Tried this with another P110 and got the same result.

So, I have now re-introduced a static for one of them, left the other as it was and will now wait and see what happens overnight.  Failing that, will do a router reboot once everyone is out of the house over the weekend and see if that fixes it.

The issue is definately DHCP/static mapping related during the pairing process

  @ferg22 update.  my bad. as I was configuring a new router, a device that I had reassigned to a static didnt switch over for some reason, so there was a clash of IP addresses which is why the P110 was denied the IP address it was asking for.

Rebooted the other device so it picked up its correct IP, and the P110 was reset and setup as expected with the now not in use IP address.