A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
This is one reason I stay away from the 64-bit version of Office.
Video files have 2 formats: a container format (indicated by the file ending) or .mp4, .m4v, etc. and a codec. The dialog is letting you know that your videos have an incompatible codec. Your container format is fine, and resaving with a different file ending can't fix this.
Office prefers videos encoded with an H.264 codec. If your video came from an iPhone, it is encoded by default with H.265, which PowerPoint cannot read. You can try converting your video to H.264 using a free online convertor, then see if that will work in PowerPoint. iPhones can also use H.264 as a video default, which will prevent this issue in the future.
If you still have a problem, search on "64-bit" H.264 codec to get a 64-bit codec for your computer.