I uninstalled all .net and launchbox
So I´ve installed from this link: https://dotnet.microsoft.com/en-us/download/dotnet/3.1
First, I installed "ASP.NET Core Runtime 3.1.32"
So I installed ".NET Runtime 3.1.32"
In the end - already sad by the situation - I installed ".NET Desktop Runtime 3.1.32".
And it worked! (Installed all as administrator, don´t know if it matters)
I don´t know if you have to install the three. My guess is that "Desktop Runtime" alone can solve the problem.
Didn´t reinstalled Lauchbox in C:\ (I´m running it separatedly from eXoDOS).