Exported files are unplayable

[#1]

I've tried to export my first project in Rush on Mac multiple times to both Local and YouTube, and the result is that the files are unplayable regardless of what player I use. The files are exported without warnings, and uploaded to my YouTube channel without any hickup, but then YouTube says it can't process the file (tried three times). On my Mac the files are unplayable in Quicktime, VLC and even if I try to import them into Rush (compression not supported). 

I used all of my three free exports trying to get one functioning file exported, then paid to be able to try again with no luck. I've tried different presets, 60 and 30 FPS with no luck. I've used the same type of video files in iMovie for years without any issues. 

The project is less than five minutes long. The source material is mainly shot on an iPhone 8. 

I'm using a 2,3 Ghz Quad-Core Intel i7 MacMini (2012) with 16GB of 1600 Mhz DD3 RAM running Mac OS Catalina 10.15.7 (19H114). 

What do I try next? 

[#2]

I've tried to export my first project in Rush on Mac multiple times to both Local and YouTube, and the result is that the files are unplayable regardless of what player I use. The files are exported without warnings, and uploaded to my YouTube channel without any hickup, but then YouTube says it can't process the file (tried three times). On my Mac the files are unplayable in Quicktime, VLC and even if I try to import them into Rush (compression not supported). 

I used all of my three free exports trying to get one functioning file exported, then paid to be able to try again with no luck. I've tried different presets, 60 and 30 FPS with no luck. I've used the same type of video files in iMovie for years without any issues. 

The project is less than five minutes long. The source material is mainly shot on an iPhone 8. 

I'm using a 2,3 Ghz Quad-Core Intel i7 MacMini (2012) with 16GB of 1600 Mhz DD3 RAM running Mac OS Catalina 10.15.7 (19H114). 

What do I try next?