So some time ago I bought a 3 pack of Deco's M5's to extended my wifi network. Was actually suprised that two units was enough 

Due to the Working From Home experience, I now installed the 3rd Deco in another part of the house. Only it won't update to the latest firmware version?

My current setup is that all 3 Deco's are connected to the ISP router in AP mode.

Main Deco and Second deco are running FW V1.4.9 Build20200924 rel 60170

Third (new) Deco is running the out of the box  FW version1.1.6 Build 20171103 rel. 47257

When i use the Deco app it and run the "update your Deco" tile, it says: "Your Deco-Home Wifi system is up-to-date. Have fun!" Normally it would mention the latest installed FW version.

Logging into the main deco, I can also see my network, and under Firmware Upgrade it shows the FW versions mentioned above, without "Latest firmware version" being filled for the third (new) deco.

What have i tried so far:

- Logon to the third deco via browser, like i can do with the first and second deco. doesn't work and i get a cannot connect to server error.

- Multiple resets of all 3 deco's.

- Reset of ISP router and 3 deco's

- Connected third Deco via UTP directly to the main deco

- Connected third Deco via Wireless to the main deco

How can i upgrade the third Deco M5 to the last firmware version? I am now missing crucial information in the app like

- How it is connected (wireless or ethernet)

- Which clients are connected to the AP

- Set MESH settings for specific clients

- See speeds of clients

- Disable the LED light on this device