The simple answer is that you have invalid configuration at .idea file. This problem may appear if you open the same project in different versions of jetbrains' IDEs, so you should regenerate the .idea file.
Close the project
Go to the folder of the project through file explorer
Delete the current .idea file (don't worry about major problems appearing after that action).
Open the project via pycharm again
Check through explorer if the .idea file generated inside the project.