MP4 file Import Error (no video)

Has something changed to Premiere Pro recently? 

I've always used the same camera video files (mp4) and screen recorded files (mp4) whenever I make videos. I've never had any importing problems with these MP4 files until today! I cannot import my MP4 video files anymore, only audio files are available on the timeline. 

I've tried several solutions that I found here, such as clearing the cache files, unchecking the acceleration decoding, and changing the mercury playback engine settings, but none of them worked.

Are there any other solutions that I can try? I don't know why it stopped working as it did before..