Sorry for the inconvenience that occurred. Can you please try deleting all PRO files, extracting the .zip file once again, and then run the client as administrator? If it still doesn't work, repeat the same procedure after re-downloading the latest version of the client from here. Hopefully, this will help you to resolve your issue.
Please inform us about the situation after doing the above-mentioned steps. We will be waiting for your reply.
Can you please try running the client as administrator and see if that works? We would be waiting for your reply.
You can also download the optional update of the client from here. It should fix the problem with Windows patcher. Remember to delete all previous files of PRO before extracting this new file.
Yverneas's post in Error while patching the game after the client downloads it was marked as the answer