Microsoft Remote Desktop doesn't connect thru Forticlient macOS

Dear All,

Our company uses forticlient and authenticator to connect to the company's network to work remote.

on MacBook Pro 2012 with Catalina it was working with Forticlient 5.x and Microsoft Remote Desktop.

Now I have a new MacBook Air M1 with Big Sur I was able to connect to the office's VPN with Forticlient 6.x and authenticator.

but when I start Microsoft Remote Desktop I got the following error :

We couldn't connect to the remote PC because the PC can't be found. Please provide the fully-qualified name or the IP address of the remote PC, and then try again. Error code: 0x104

i have tryed to connect thru PC name and IP adres, and both result I a error.

when I try to Ping to my office IP adres there is no result.

when I go back to the MacBook Pro with Catalina and Forticlient 5.x everything is working.

what is going wrong ?

I hope someone can help.

Grtz Manfred