Windows 64-bit OS does not always have the codex for the file to be loaded correctly.
- Set Ableton to run as Admin by default. Link below will walk you through the process. https://help.ableton.com/hc/en-us/articles/209072049-How-to-run-Live-as-Administrator-on-Windows
- Install the video codecs from the link below.
- Launch Ableton as admin; see step above.
- On the left side add the folder that has the video you want to bring in.
- Then hit "Tab" key or go to view and change to arrangement mode (KEY STEP for having the Video appear)
- Drag video from folder within Ableton to the track you want it on