Video downloading as black screen - correct time/length but no sound and no images

[#1]

Hi everyone! Many thanks for your help in advance.

I have used Premiere Pro for basic videos before (just joining, cropping sections out etc) and had to do a more sophisticated version for a work project. My more sophisticated one has video, background music, voiceover and images with text and transparent background. I heard these may be causing the problem so I embedded them and rendered... (if thats the correct terminology!) but this still hasn't helped. I exported them in H.264/High Bitrate which is what I normally use for my videos and has been fine. Only difference I can think is that I am now using a newer Mac with the 2020 version of Premiere Pro as before I was using 2015 Mac with 2018 PP software - not sure if this would affect the export process though.

Sorry if I have not explained it very well but would anyone be able to help me please?

Thank you!! 

[#2]

Hi everyone! Many thanks for your help in advance.

I have used Premiere Pro for basic videos before (just joining, cropping sections out etc) and had to do a more sophisticated version for a work project. My more sophisticated one has video, background music, voiceover and images with text and transparent background. I heard these may be causing the problem so I embedded them and rendered... (if thats the correct terminology!) but this still hasn't helped. I exported them in H.264/High Bitrate which is what I normally use for my videos and has been fine. Only difference I can think is that I am now using a newer Mac with the 2020 version of Premiere Pro as before I was using 2015 Mac with 2018 PP software - not sure if this would affect the export process though.

Sorry if I have not explained it very well but would anyone be able to help me please?

Thank you!!