EDIT: It is only .NET 4.8 required for the current ASCOM bojan.
Version 4.85?? As far as I'm aware 4.8 was the last "4,x" version before moving to .NET 5, just getting the standard monthly fixes update. You can download an offline installer package for 4.8 from MS here:
https://support.microsoft.com/en-us/...3-aa3c3e7495e0
Hope that helps - Mark