I am trying to add a MOV file to PE 12 I and keep recieving and Add Media Failure Error stating "The Importer Reported a Generic Error". I have added other MOV files without any issue so I don't know why some MOV will work and others won't. The only common characteristic I've found is that the MOV files that won't work are files that were recorded with my SLR camera. The location of the files I've added/tried adding are on my external hard drive.
Try importing a few of the problematic files from a Local Disc C location like Videos and determine if problem presists. How is the external hard drive formatted, NTFS or FAT32?
Do you have the latest version of QuickTime installed on your computer with Premiere Elements 12? And, on what computer operating system is Premiere Elements 12 running? Are you running QuickTime and Premiere Elements 12 as Run As Administrator and/or from a User Account with Administrative Privileges?
What specifically is the video compression for the problematic files? And, what is the brand/model/settings for the camera that is recording these videos?