And to resolve this issue, it is must verify is .net core 3.1 and 2.1 are on your machine. Please use the below command to verify
dotnet --info (PowerShell as admin)
If not then please install from below
https://dotnet.microsoft.com/en-us/download/dotnet/2.1
https://dotnet.microsoft.com/en-us/download/dotnet/3.1
Once installed, run horizon instance again.
The above same issue you may also face with Sitecore Identity server and solution will be same.