Some of my layers are showing up invisible in Premiere

[sofiaarias]

I'm making a simple remote music video, so I have about 15 layers of video with different entrances. Two of them were invisible when I dragged them in and tried moving them/repositioning them. They only appear when I press play. I assumed because of this, the video will be fine after exporting, but those two layers are gone after exporting. How do I fix this? 

[Michael Grenadier]

Please tell us your system specs: OS version, Premiere version, amount of RAM, Hardware specs including graphics card and your source properties and sequence settings.  You might try "smart rendering."  In your sequence settings, set your preview format to a high quality format like prores 422 and render your timeline.  Is everything visible?  If so, when you export, make sure "use previews" is checked.

[sofiaarias]

I'm using MacOS Catalina (Version 10.15.6), Premiere 14.4.0, 4 GB RAM, 1.6 GHz Dual-Core Intel Core i5 processor, 

Intel HD Graphics 6000 1536 MB, and I don't know what source properties are. Everything else is visible just not 2 layers. 

[sofiaarias · Accepted solution]

I fixed it. I had to convert it from .mov to .mp4, even though half of the other layers are also .mov