I just installed Premiere Pro from CC version 12.1.1 (build 10) on my mac book pro 2017 (high sierra 10.13.3, Intel HD Graphics 630 / Radeon Pro 555).
Double clicking .mov files in Finder opens and plays them fine in QuickTime.
Starting a new project in PP (Assembly->Media Browser-> double click) does NOT show video in the PP Source window. The video appears like it is an audio track.
The .mov file is H.264, AAC, with resolution 2316 × 892.
I wonder, but it seems unlikely. The author of that thread says:
Most of the codecs from the Quicktime 7 era haven't been used much for over a decade, so chances are slim that you'll run into this problem.
I'm working with a .mov file that was just created on a modern Windows machine. It plays fine on my Mac with Quicktime player.
Can you share the file with us...I use Mac book pro OS X 10.13.4 and just tested again to cross-check premiere pro cc v12.1.1 imports the .mov with codec h.264 fine and playback fine with video & Audio.