You can solve the problem by the link which provided by @S.Sengupta .
Or else there will be a chance that the Git inside the Visual Studio getting your new project as the old one . I got the same problems many times . So, i will tried the following steps for solving that problem.
- tried to open the visual studio as "Run as administrator" and tried to open the solution
OR
- open the solution by open with VS Code or the Visual Studio and then it will work
OR
- Trying to Re-clone the repository.
OR
- Simply checking the manual folder which are not included in the project or which are hide inside the Git
you can say.
I hope this one is helpful for you.
Even if none of the above is working then try to clean the project or tried to clean the git by diff. Git commands for the command line and try to re-clone the project directory.