Hello everyone! (Longtime lurker, first time poster…)
This was quite a tricky case - I tested dozens of potential render settings combinations to find something that worked. For some reason, Adobe decided to discontinue the codecs necessary to render alpha channels, and there isn’t an alternative codec that functions the same way the legacy PNG codecs did within our software. Unfortunately, this means that Adobe’s Creative Cloud software (AE and AME) is no longer a viable option for exporting transparent video that is compatible with our software (for the time being).
But wait, I still come bearing good news!
Sony Vegas Pro still has the necessary quicktime codec needed for transparency!
Here are the export settings for Vegas Pro 16.0:
- Import the video
- Right click on it > Properties > Media > Alpha Channel: Premultiplied > OK
- File > Render As
- In the dialog box, choose Quick Time 7 - 512 Kbps Video (Kbps will determine the quality and size)
- Click on Customize Template
- Select Video Format: PNG / Compressed Depth: 32bppp color > OK
- Click on Render
Just a note, this is only possible with .mov files.
I the meantime, we will be looking into finding a more compatible render mode for the more recent Creative Cloud software in the future, and we will be updating our Help Center page to reflect all of this information.
Thank you all so much for your patience and understanding while we tested this issue. We greatly appreciate it. 
Helen