Ok, U...so here's the deal. I started using the steam version myself very recently - mainly due to win10. I recently jacked around with it trying to get BUFFY to work with it for a GOTM (this was known issue with the Steam version, but irrelevant to me until I started using it recently)
So, BUFFY runs with the beta steam version, but the issue related to what I mentioned earlier about different assets when opening a pre-existing save, like say a Game of the Month generated by GOTM staff that don't use the Steam version. Or in your case, likely the same deal but with a HOF game created by some else not a steam.
It boils down to the simple fact that the Steam version has a different DLL. I narrowed down the issue based on some stuff I'd done for HOF and some work Neilmeister did trying to get the HOF mods (van,warlords,bts) to work for GOTM saves.
Bottom line, all you need is a copy of the original non-steam dll. I lay this all out in a post over in a GOTM game here:
https://forums.civfanatics.com/threads/news-botm-144-starts-december-9th.625166/page-3#post-14952098
The DLL switchers are something I've been using a long time. You don't have to use those, but they are nice. However, the main thing is that before you copy over the DLL contained in the zip, make sure you rename the existing DLL.
(oh..i had attached winrar files, but in a post below that I attach some regular zip files)
Sorry I should have immediately noted this when you first mentioned Steam, but you kinda jumped to another issue about not loading this that or the other.