I checked all the solutions and found that in most cases the "Change project location" form worked in 80% of cases. But for the next 20%, I would recommend doing the following:
Modify the Project folder and then import it. (do it first)
If the above does not work, rename the project and try importing it.
If you have not succeeded yet, check if you are importing the project from one workspace folder to another or not. IF yes, then when importing projects, check the box "Copy project to workspace".
And even if you have not succeeded, clik import -> General -> An existing project in Workspace.
PS → If this solution worked for you, please vote because I am new here and therefore need this to participate in basic questions and answers. 
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