Launcher-related problems can often be resolved by repairing your .NET Framework installation.
Please download the appropriate version of the .NET Framework from the Microsoft website linked below. The installer should then prompt you with an option to repair your installation.
Be sure to restart your PC afterwards!
Windows 10: NET Framework 4.7: https://www.microsoft.com/net/download/dotnet-framework-runtime/net47
Windows 7: .NET Framework 4.5.2: https://www.microsoft.com/net/download/dotnet-framework-runtime/net452
If an error is displayed referencing that a later update is already installed, instead download and run the .NET Framework Repair Tool from the Microsoft website: https://www.microsoft.com/en-GB/download/details.aspx?id=30135