Can't install the installer... .NET framework missing? HELP!

Hey everyone,

it’s a nightmare. When trying to install my purchased Cubase 11 Pro Upgrade (from Cubase 7 to 11) the Steinberg Download Assistent tries to start a Setup.exe which itself keeps asking for the (completely outdated) .NET v 4.0.30319. I’m running Win10 and I cannot install another framework because the .NET framework installer says that the .NET framework is already installed!

Can someone please help me? Thanks a lot in advance!
Tommy