I had a network of six M4's. The M4's are all on firmware version 1.8.2. Build 20251027 rel. 36896.  I wanted to expand this network, so as TP-Link say all their devices are compatible, I bought three M5's. 

The main deco is in access point mode, as I have a separate PC that handles the firewall. This is connected directly to my internet router that is in bridge mode.

The M4 network has been working for years. Occasionally the app shows a device offline, but after a refresh a couple of times it sees it.

I added one M5 to the network, which took a long time. It was never seen by the app on my phone, either wirelessly or with bluetooth. Eventually, after restarting the app, the M5 and my phone several times, it magically showed up and I could add it to the network. I was then prompted to change the main deco from the M4 to the M5, as apparently it's not good to have a "lower" device as the main deco.

I eventually managed to add one more M5. This was similarly hard to do, but eventually it was added.

The M4 that was the main deco is currently switched off.

Now I have a network of five M4's and two M5's, one of which is the main deco. All the devices show green. The internet is working for all devices. They are all online, but the app shows all of them except the main deco as being offline. Yesterday they all showed online.

I have rebooted them all. Still the same.

It seems to me that the app has some serious bugs in it.

Anyone any ideadsas to how to see all my devices?