Plug inaccessible - could it be the TP-Link extender 8630P

Plugs which were accessible via Homey have become inaccessible in other parts of the house but remain accessible close to the router.
Kasa finds them OK.
They have static addresses.
Router shows them in DHCP client list
They can be pinged correctly - with very short response times
WiFi analyser shows very strong signal at the distant locations
but Homey does not control them.

I have repeatedly rebooted, re-paired the plugs (need to enter the IP address because H does not find it) and even re-registered them on Kasa.

I see that other people have had problems with these plugs but wonder whether the issue here is that when they are distant from the main router they have logged on to the extender and this is not passing the correct data back to the router/Homey. I have read that some extenders apply their own private NAT when they are cloned to use the same SSID as the router which they are extending.

I have not yet moved to Homey 2.0 because of the risk of losing direct voice input (on my other set up Alexa mishears invocations meaning the several flows have become unusuable). The network is 192.168.x with an x that is neither 0 nor 1. Everything else on the network functions as before.

It may depend on the protocol that the plugs use to communicate with Homey.

Sorry i should have said they are TP-Link plugs (HS100 and HS 110 - both have the issue) and the router is also TP-Link (WR940L). So it is a continuous TP-LINK environment, and as I said the Kasa application controls the plugs when they are at the distant - extender linked - location as well as when they are close to the router - which is right next to the Homey.

From the app page I gather that you can either use fixed IP-addresses or have the app discover the devices automatically. Which route are you taking?

Discovery produces no results so I have assigned static IP addresses to the plugs and inserted these in the Homey app as advised. The plugs were working fine with that last year. These appear in the DHCP client list (see my first post) and they can be accessed with ping (ditto).

I have also tried the option in the app for Homey to re-establish IP address on reconnection; no difference.

Kasa does not report IP addresses but I have checked that the MAC addresses of the plugs are the same as reported by Kasa when switching on and off and by the router when displaying client list.

In that case, the combination of the extender and Homey is likely causing some sort of networking issue preventing Homey to be able to find the devices. Because Homey is a black box, there’s not much you can do to debug that.