Compressor - Error trying to open source media file.

This post is about an error message with the latest version of Compressor. Not sure if this is the correct location to post this, but I discovered that I cannot post in the Compressor forum as it's archived.

First time trying to import GH4 video files into Compressor v4.4.1. The rec format is MP4 (LPCM), rec quality is 4K, 100Mbps, 24P. My goal is to transcode these files to ProRes for smoother playback. Not sure whether FCP X can play these files smoothly at native format and resolution. When dragging and dropping the file into the "Add Files" area, I'm getting a message "Error trying to open source media file." As a workaround, I tried the menu bar > File > Add file. I'm at a loss of what to do. I would expect Compressor to be able to read this file easily, considering the popularity of the GH4.

I used to use a cracked version of Compressor, I hope that's not the reason. I used AppDelete to delete the app and related preferences files and deleted them, then reinstalled a paid version from the Mac App Store. I'm wondering whether I should have restarted after deleting.

Any suggestions would be most appreciated!
HL

Do the files open in QuickTime Player X? If QTX can't open it then that's an indication that it's not supported natively by AV Foundation.

My software:
Pro Maintenance Tools - Tools to keep Final Cut Studio, Final Cut Pro X, Avid Media Composer and Adobe Premiere Pro running smoothly and fix problems when they arise
Pro Media Tools - Edit QuickTime chapters and metadata, detect gamma shifts, edit markers, watch renders and more
More tools...