At the moment, Movavi Software does not support HEVC (H.265) decoded files, due to the difficulties with their licensing scenario and the inability of their playback for most devices and browsers (e.g. Google Chrome, Firefox).
You can learn more about this matter here: https://movavi.io/what-is-h265-en/
However, most macOS devices are equipped with a convenient workaround: the feature for decoding HEVC (H. 265) files is built-in and does not require any additional software.
To encode the video file, right-click its icon and choose the ‘Encode Selected Video Files’ option:
Next, select the most suitable resolution with H. 264 codec and press the ‘Continue’ button:
After following these simple steps, the resulting video can be edited or converted in Movavi software.
If you are receiving a "Cannot open files" error after trying to import the converted files into Movavi software, it's most possible that the conversion process has not been completed yet.
You may check it through cogwheel button on the system taskbar in top-right corner of your screen:
