If you don't mind using that standalone version, I can get you a key for it. But there's one other possible cause I can think of for the Steam issue: does your Windows username have any non-English characters in it? Steam can behave oddly when it runs into that while trying to write to that specific location, our tech support gets a lot of Korean and Taiwanese people playing OOTP that have that issue, and the usual solution is to install it to a custom location that avoids that name in the file path.
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