If you just want to start the game, you can bypass the launcher with the bypass_launcher "beta" on Steam.
As for the error, there's some dependency missing for the embedded browser they use in their launcher. This might be because you don't have a recent enough .Net Version installed, or missing some sort of VC++ redistributable.
https://support.fatshark.se/hc/en-us/articles/360021423613--PC-How-to-Resolve-Most-Launcher-Issues