AVM Fritz: WLAN Mesh with Powerline Repeater does not work

Today i upgraded my FritzBox to FritzOS 6.90:

After the upgrade of the FritzBox i tried to upgrade my Powerline Adapter. But the 6.90 was not shown with inside the update mechanism via GUI.
(Be careful: you have to update your FritzBox first:
https://avm.de/nc/service/downloads/download/show/18332/:

ACHTUNG: Bitte nur installieren, wenn Sie eine FRITZ!Box mit FRITZ!OS >= 6.88 verwenden!

)

So i downloaded the firmare image via this link and installed the new version:

Inside the FritzBox the WLAN mesh can be checked in "Heimnetz -> Heimnetzübersicht":

But no device behind the powerline adapter showed up.
I googled a bit around, but all AVM support pages where deleted. Inside Google cache i found the following:

So the mesh icon is missing at the powerline adapter. A reboot of the fritzbox and the powerline adapter did not change anything.

On AVM website there is an image how it should look like:

 

But it think, they have a problem with their mesh functionality and removed the 6.90 auto update for the wlan repeaters/powerline adapters and they even removed all support pages for the wlan mesh.

Let's wait for some bug fixes ;-)

(Still remember: These upgrades are just for free)

EDIT: Read the next attempt here.