I have 2 HS110 smart plugs but the app now no longer works on a bridged connection in this scenario:

Let's call the main network Network A and the bridge network Network B

Network B is bridging Network A

The smart plugs are on Network A

The mobile device with Kasa is on Network B

The devices on Network B can contact devices on Network A but not vice-versa.

My speculation is the problem this now causes with Kasa is that it assumes the devices can be reached both ways. But the plugs fail to send data back to the mobile device on Network B. This results in a "failed to resolve command" error on the app. The only way then is to switch WiFi off and use mobile data. This also causes a much longer first response time when using mobile data as the app now waits to timeout after 30 seconds before using it over the internet and start working. I thought the app was broken at first because it was taking so long. It seems this change was done server side as I hadn't downloaded any updates before getting this problem.