Have a solution, call is Solution_A which contains 16 projects. They all work correctly. Created a second solution, Solution_B. In Solution_B added an existing project from Solution_A. When I look at the references in Solution_B all references have a yellow marking. They do not have a path associated with any of them. This includes the System.dll reference. I have added new projects to Solution_B and they are fine regards to the references. I have tried to add the System.dll manually and it ends up with the same issue.
I have double and triple checked the .NET Framework is the same.
If I build the solution (or the project) I do receive an error about missing nuGet packages. In my thinking this does not explain why System.dll is causing the warning.
Any suggestions on how to correct this issue? or a way to receive more information on why this is occurring?
Using VS 2019.
Thanks for the assistance. Duane