Delta_Yukorami, the Civ3 - Technical Support Forum is full of posts with "File not found" messages:
https://forums.civfanatics.com/sear...t&c[child_nodes]=1&c[nodes][0]=48&o=relevance
Normally these messages show, what file was not found, making the search for the error much easier. But in my search in the Civ3 - Technical Support Forum there are also several posts about exactly the message
file not found "#". As far as I can see, none of them was answered with a proper solution in many years.
So, at least with such a small amount of information, I can only post here a
guess. I think here something fundamental went wrong with the construction of your scenario. One possibility could be, that in the pediaIcons file in the text folder of your scenario something went wrong.
Normally all entries in that file start with # , followed by the description of that function.
It could be, that here one of those descriptions was cut out in that file, so that there only left the #.
An other reason could be that in the biq of your working scenario you set download paths to other Civ 3 folders and forgot to set them in the biq of your new scenario, too.
As said, only guesses - no knowledge.