You should post this in the tech support forum(ideally with a working screenshot).
If you got the error which I think you got, it can have many sources. To narrow it down somewhat, try to start the game from eu4.exe (eu4.app on macOS) . If that works it is a launcher problem. If it doesn't work it is a game problem. In that case, please tell me how far in the startup process you get(what is the last thing that eu4 displays) and if you get any error message.
If you get an error message about a missing VCRUNTIME or other dll file, please try to (re-)install the microsoft visual c++ redistributables. You can get the latest version from
this website or directly download the installer from
this link. There is an arm version(ARM64), a 32bit version(x86) and a 64bit version(x64). Current eu4 versions only need the 64bit(x64) version.
After downloading it, you have to run vc_redist.x64.exe to install them.
Does this help?