Hello and welcome to Techspot.
If the file that you`re trying to post contains urls. That may be the reason that you can`t post it, as you will not be able to post any urls untill you have at least 3 posts. This is Techspot policy in order to deter spammers.
What you can do however, is attatch the file as a text file by going to the manage attatchments section and uploading the file.
Regards Howard :wave: :wave: