how to fix is relatively simple
locate the mod folder - usually in C:\Users\<insertnamehere>\Documents\My Games\Ironclad Games\Sins of a Solar Empire Rebellion
download a copy of STA3_final_edition if you don't already have it
upload file to https://filepost.io/
get you friend to make sure the game is in vanilla mode
download file extract and put in above folder. this way all the files you share are identical in every way. this cures the host file discrepancy error.
please pass this on to anyone else with this issue