Invalid Python SDK in PyCharm
Dealt with the same issue despite using python and pycharm without issue for months. Recently kept giving me the error despite changing the PATH variable of my system and even manually pathing within pycharm. After hours of reinstalling pycharm, python and even jumping around versions with no success it turned out it was because my python directory had a space in it that it just randomly decided to break.
For anyone who has tried what seems like everything to no avail ensure that NO part of the path to your python directory contains spaces