Premiere Pro 2020 Won't Import Some .MP4 Files After Windows Reinstall

I've had Premiere Pro CC running fine on Windows 10 Pro.  I've had to reinstall Windows and subsequently, reinstalled CC. 

Now some MP4 files that worked in Premiere Pro prior to the reinstall no longer do.  Premiere shows a "generic error" when trying to relink the files in an existing project, and an "unsupported codec" errors when trying to report them manually.  The previous version of Premiere Pro CC (2019) on the same machine was able to handle these files without problem.

Here's an example file info dump from MediaInfo:

General
Complete name : D:\Projects\RPXD0031.mp4
Format : MPEG-4
Format profile : JVT
Codec ID : avc1 (avc1/isom)
File size : 240 MiB
Duration : 1 min 49 s
Overall bit rate mode : Variable
Overall bit rate : 18.4 Mb/s
Encoded date : UTC 2018-08-02 02:17:23
Tagged date : UTC 2018-08-02 02:17:23
AMBA :



Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L4.2
Format settings : CABAC / 1 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 1 frame
Format settings, GOP : M=1, N=8
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1 min 49 s
Bit rate mode : Variable
Bit rate : 17.9 Mb/s
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 100.000 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.194
Stream size : 235 MiB (98%)
Title : Ambarella AVC
Language : English
Encoded date : UTC 2018-08-02 02:17:23
Tagged date : UTC 2018-08-02 02:17:23
Codec configuration box : avcC

Audio
ID : 2
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : mp4a-40-2
Duration : 1 min 49 s
Bit rate mode : Constant
Bit rate : 128 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 1.67 MiB (1%)
Title : Ambarella AAC
Language : English
Encoded date : UTC 2018-08-02 02:17:23
Tagged date : UTC 2018-08-02 02:17:23

Clearly something that was installed on the machine prior to the Windows reinstallation was providing playback support for these files to Premiere.  But I'm stumped as to what it might be. 

Any suggestions would be greatly appreciated.