Microsoft made a commitment to provide 10 years of product support for Windows 7 when it was released on October 22, 2009. This 10-year period has now ended, and Microsoft has discontinued Windows 7 support so that we can focus our investment on supporting newer technologies and great new experiences. The specific end of support day for Windows 7 was January 14, 2020. Technical assistance and software updates from Windows Update that help protect your PC are no longer available for the product.
https://support.plex.tv/articles/naming-and-organizing-your-tv-show-files/
https://support.plex.tv/articles/naming-and-organizing-your-movie-media-files/
MP4 Files:
New Agent:
Old Agents (upgrade - now - Old Agents are no longer supported):
- upgrade to Windows 10 <—Free <—best Windows I’ve had (be glad you skipped 8).
- name and structure your files correctly
- deny Plex the ability to look inside MP4/M4V files and PREFER embedded title fields over correctly named and structured media items (much easier with the New Agent).
Comply with those requirements and your experience will greatly improve.