The path is not a legal form when opening a project

The path is not a legal form when opening a project

I was trying to open a project to look at the source control. When I tried to open it I noticed that none of the projects opened.

since all the projects were unloaded I right clicked on a project selected Reload Project. I got this error

To fix this I opened a terminal window (could use powershell or command prompt) and typed the command dotnet –version

finally I looked in the directory when my solution was located and opened a file name Global.Json

{
  "sdk": {
    "version": "3.1.101"
  },
  "msbuild-sdks": {
    "MSBuild.Sdk.Extras": "2.0.54"
  }
}  

And modified the sdk version to match the dotnet version I have installed

 {
  "sdk": {
    "version": "3.1.401"
  },
  "msbuild-sdks": {
    "MSBuild.Sdk.Extras": "2.0.54"
  }
}  

I was then able to load the project