Format Factory 2.40 Mobile Output problem...

So, I'm having this really bad frustrating problem with the new version of Format Factory.
When I was using 2.30, and converted it into the mobile format, i had no problems at all.
Then when I installed 2.40, and converted into mobile format, and then put the output into my phone, it wouldn't work. The .MP4 file would be on my phone, but when I open it, it would just be a black screen. 2.30 had no problems, but 2.40 did.
I need help please.