I am short on precision, but let me try.
For now, one of you host, and when that works you can do mutual hosting.
Each player always opens their game using the run as admin option. This is essential in Windows 10.
The host creates the game and sends the opponent's trn file. It is essential this file is sent via zip, rar or dropbox so it is not corrupted. It is very important for the host to make a copy of the opponent's trn file, but keeps a copy in the host folder.
Both players make their moves and create their ords and save.
The opponent sends the ord file to the host.
The host places the ord file in his game folder.
When the host opens the game and looks in the load menu, the game will show with both sides displaying a red paperclip.
The host selects his faction to open the game and runs the turn.
He then saves.
Now it is time to send new files to the opponent.
When this does not work, please repost what you have done.