MusicCast Device can't connect to Audience

Hello,
I have the following problem with my Audience Router.
My Technisat Radio 143 and my Yamaha NX-N500 do not connect to the router. The broadcast WLAN is displayed, but a connection is not established (the Technisat has a display that shows the WLAN) regardless of whether I enter the connection data or use WPS. No connection.
A standard FritzBox works straight away.
All my computers and cell phones work without any problems.

Does anyone have any idea which settings I should check?
At least the NX-N500 should already be connected to someone.

Thanks for all the tips
Mathias

Translated with DeepL.com (free version)

Ich kann die WLAN Spezifikationen Ihrer MusicCast Gerat nicht finden, um Ihnen einen Anhaltspunkte zu geben.

I cant find the wireless specifications of your MusicCast device