Today, for the first time, when I try to launch the Quentinc tlient, I receive the following message.

Fatal error dialogue unable to initialize application environment

Any idea how to solve this problem?

Hello,

This is a very special error, I need much more info to help you.

tell me information for your computer, what kind of windows u use, 32 or 64 bit. once I got this message but I reinstalled playroom and it's was ok

I have experienced this problem sometimes, and I can say that this issue happens especially when you do not have a good internet connection, or when you try to play so fast. This can occur especially in uno, when playing with interceptions and other rules. That's not any problem which needs so much work to understand where does that come from, but if you are experiencing this problem at the first time when you connect to the server, try to connect again and again, or reinstall the Application.
Hope it works for you as it worked for me as well.