Unable to view exported video

If your exported H.264 (MP4) files won't playback in QuickTime player (or another player) something has gone wrong with your export.

More details (as Ann requests) would be useful for others to respond and perhaps figure out what is going wrong in your situation.

But in the short term try this as a workaround.

Export from Premiere Pro using (say) Prores - in the export panel you want to choose Format - QuickTime, Preset - Apple Prores 422. 

Once that file has been fully exported open it in QuickTime player or import it back into Premiere Pro to test it is all plays OK. If it plays fine open Media Encoder drop the Prores file there and select H.264 from the format list and then choose your preset (say) 'Match source, High bitrate' or the 'Youtube 1080p Full HD' as examples. Render. Do you now have a working H.264 (MP4) file?

Post back with further issues.

QuickTime player *will* play H.264 (MP4) files. While there are some issues in various situations playing H.264 on Macs that I won't go into here - not playing H.264 'at all' is not one of them. VLC is a fine option if you do have issues with QuickTime Player and something any Mac user should have installed as a secondary playback option.

Post screenshot export settings.

Yeah, H.264 isn't compatible with the QuickTime player. If you guys all use Macs, you probably have a way to view them threw another video player. Anyways,  you can download a free video player application like VLC (very well known and easy to use) https://www.videolan.org/vlc/

Then you just open your video files through VLC and you are good to go!

If you have a team of people that all use Macs with H.264, and nobody else has this issue, ask around. See if people use other video player apps. Because they can't be using QuickTime.

If you don't feel like installing VLC or if your company instructs you not to, exporting in QuickTime or ProRes will be a better option if you are able to do that.

Furthermore, an ACP will know more about this, but hopefully, this helps!