Hello @opal1974, please add PROTON_LOG=1 %command% to the game's launch options and drag and drop the generated $HOME/steam-$APPID.log into the comment box.
err:mscoree:CLRRuntimeInfo_GetRuntimeHost Wine Mono is not installed in the log points towards #18.
In the new 4.2.3, the game now launches due to the .net fix, but the steam overlay doesnt work with it. IIRC, some of the DOSbox games are like this in windows, so maybe it isnt a bug
PROTON_LOG=1x1 2019-04
Compatibility Report
System Information
I confirm:
Symptoms
Game crashes upon launch. Installs fine.
Reproduction
Install game, won't launch either into game or options. .net launcher issue perhaps?