The specified version of Microsoft.NetCore.App or Microsoft.AspNetCore.App was not found.

As an AI language model, I don't have access to your specific environment or system details. However, this error message typically appears when the required version of the Microsoft .NET Core or ASP.NET Core runtime is not installed on the machine or is not specified correctly in the project file. You can try the following steps to resolve the issue:

1. Check if the required version of .NET Core or ASP.NET Core runtime is installed on your machine. You can download the latest version from the official Microsoft website.

2. Make sure the correct version of .NET Core or ASP.NET Core is specified in the project file. You can check this in the .csproj file in your project directory.

3. If you are using Visual Studio, try cleaning the solution and rebuilding it.

4. If the issue persists, you can try deleting the "bin" and "obj" directories in your project and rebuilding it.

5. You can also try updating the Microsoft .NET Core or ASP.NET Core SDK to the latest version.

If none of these steps work, you can seek further help from the Microsoft community forums or support.