Hi @Adrien_Colson welcome to the Zwift forums.
I’m looking at your session logs on our server, and see the last successful session on January 21 (Windows10).
By any chance, is your iMac running the OSX v10.15 Catalina? Starting with this version of OSX, Apple changed the way permissions work for security reasons. If so, please see this previous thread for the likely solution.
If you’re running an older version of OSX, we can troubleshoot further.