If you receive an 'Oops' error when attempting to import to the editor via the 'Add Media' button within the editor, this may be solved by converting the file you are attempting to import. We recommend that you convert your files to MP4s on this site https://cloudconvert.com/, and that should solve things for you!
If you are receiving an Oops error when attempting to import via the 'Open in Editor' button on the Video Management page, please refer to this article: I get an 'Oops' error when clicking on 'Open in Editor' on the Video Management Page
If you are still having an issue after doing the above, please reach out to support@screencastify.com