Check this out to learn what Cubase supports:https://helpcenter.steinberg.de/hc/en-us/articles/115000808250-Video-support-in-Nuendo-Cubase-WaveLab-and-Dorico
Also, note the the file extension indicates the container, not the video format. You might have to convert the file. https://audiospot-creativetools.com has a good cheap converter that’s easy to use.