Error importing .mov Alpha video

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#1

Have you searched the Docs and Knowledge base?
Principle Version:Version 5.14 (5026)
macOS Version:Big Sur
Sketch Version: non-applicable
Description of what you need help with:
I’m trying to import an Alpha .mov video to principle and it only brings a grey square, no video. Tried to make the file lighter but nor really working.
Exported as Animation RBG+Alpha from After Effects.
NOT TRYING TO SEE IT IN MIRROR.
Steps to reproduce the behavior:

  1. Export video to RBG+Alpha from AE
  2. Drag to principle
  3. Grey square appears.

Screenshots/Sketch File/Principle file: (if applicable)

#2

See this: Can't play .MOV in iOS app - Critical