Removing Audio Tracks

Hello,

I have a movie file that has two Italian and one English track. I’ve used the MKV Tool to disable the two Italian audio tracks and I dragged the English track above them (ID still stays 3). I then start the multiplexing, it exports the file and if I play it, I now hear the English playing.

BUT, if I were to drop it into DaVinci Resolve, the audio track is completely missing and i cannot figure out why that is. If I open the file in VLC I hear the audio but in DR. No audio track. I need to switch the file over to MP4 by the way.