How to solve the problem with .NET Framework?

Question

.NET

When installing programs, this window pops up. Installing a more recent version of .NET does not help, the same error occurs, or when installing the same version 4, information appears that this version is already installed

Answer 1

What kind of program is that?

Mathcad Prime 3.1
MATHCAD PRIME 3.1 NET.FRAMEWORK 4.5 and 4.6

Answer 2

Try Repair for version 4.0

Answer 3

The Microsoft .NET Framework Repair Tool may help