Preview for MOGRT files will be generated if there be a MP4 file with the same name beside the MOGRT file which Motion Factory will use it as a preview file.
For solving the preview issue, please make sure about the following requirement:
1. The MOGRT file and the MP4 file are having the same name.
2. There isn't any dot in the name of the MOGRT file and the MP4 file. ( except the last dot before file extension )
After all, if the issue still exists, you need to copy the content of the folder (which you want to import it in Motion Factory) into the new address on your device.
Then try to import the content by using Motion Factory.
Hope this article helped you, for more information visit Pixflow help center