Hello, and welcome to digitalfaq.
h264 encodes of 1920x1080 at film speeds of 24/23.976 fps have the same format parameters for both PAL and NTSC. Reworking video in something like Premiere will make it region free (what region do they use, BTW?). BluRay has specific structure requirements. The fact that the source is mp4/h.264 doesn't mean that those requirements are being met. What difficulties are you having, specifically, other than audio?
We could use more information about your source. Did you notice the message halfway down the dialog window in MediaInfo (at the arrow)?:
On MediaInfo's top menu bar, Click on "View" and choose "Text" view. From the window that displays, you can select the text of the entire report, copy to the clipboard, and paste the entire text into a forum post.
One problem might be the source audio. AAC audio can't be used for BluRay. Note also that mp4 containers are not BluRay compatible. Looks like some re-processing/resampling will have to be done.
A general summary of BluRay HD, SD, and UHD specs is here: http://www.videohelp.com/hd#tech
More detail about encoding and other requirements for standard h.264/MPEG BluRay: http://forum.doom9.org/showthread.php?t=154533
, if it helps clarify matters. The last link is rather techy stuff, but the final output for encoding/authoring has to meet those requirements.