A media file with an ! on the timeline means that KineMaster is unable to locate the image or video. This happens when the image or video is moved to another folder, deleted, or renamed.
If you try to preview or export a project with a missing file, an error message will alert you that some media files in the project are missing.
You can fix projects with this error by doing the following:
1. Locate the video or image you imported into your project, then put the file back in its original location
2. Delete the missing file from the project if you don't have the original file anywhere else
After doing one of the two above, you will be able to preview and export your project normally.