OK, so now we know it's not user error, we can start trouble shooting.
I know it's a complete pain having someone go through steps with you that you have already done, but best to check just in case, hat way we're all on the same page and nothing gets missed
Your best bet would be to do as Myke said, either send him a link to the itch.io download, or put it on drop box and send him the drop box link, he'll be able to download it and check if he can see anything wrong.
Just a thought, did it work from the .exe before you uploaded it to itch.io? If it did, then it might be soemthing that's happened on their end, maybe a corrupted file.
Primary Desktop:
i7 7700,k NV1070 8GB, 16GB 3200mhz memory, 1x 2TB Hybrid, Win10.
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