EX6400 Firmware Version: V1.0.2.164 suddenly does not connect to HPhp-color-laserjet-pro-mfp-m176

Hello, we have for quite a long tome a AC 1900 installed and to that a hp-color-laserjet-pro-mfp-m176.

Suddenly the printer does not print anymore as it seems it will not get connected via the AC 1900 to the network.

We changed and updated firmware for printer + AC 1900

- printer works fine if connected directly in Fritzbox from all laptops/phones

- connection to the internet works fine if connected via AC1900 as good as through Fritzbox connection

- AC1900 has IP Adress and is seen as prt of the network and is accessible for any configuration....

We are at a loss and cannot think of anything else.

Any suggestions please?

Thanks

Birgit