I was unable to install SupportAssist on my Alienware R12. The windows event log said I was missing .NET Framework 5.x and pointed me to this link: https://dotnet.microsoft.com/en-us/download/dotnet/5.0/runtime?cid=getdotnetcore

I installed .NET 5.0 and rebooted. Afterwards, I was able to install SupportAssist.