Two files ending in .mp4 can contain differently encoded video or audio. The filename alone therefore cannot establish that PowerPoint can use a clip. Start by identifying the actual media format rather than repeatedly changing the slide.

Keep the original recording and work with a presentation copy. Record its duration and whether it contains speech, music or essential on-screen text. Those details give you a useful comparison after any conversion.

Check the encoding, not just the extension

For current desktop PowerPoint on Windows and Mac, Microsoft recommends an MP4 file containing H.264 video, also called AVC, and AAC audio. If the current clip uses an unsupported encoding, export or convert a copy with compatible settings using a tool you already trust.

Renaming a file extension does not re-encode its contents. A file made to look like an MP4 by renaming can remain incompatible and become harder to identify.

If the converter exposes separate video and audio choices, inspect both. A visible picture with missing speech is still an unsuccessful conversion for a narrated demonstration.

Verify the clip in the actual deck

Insert the converted copy into a test slide and run the slideshow. Play the beginning, a section in the middle and the ending. Check speech clarity, picture proportions and whether small text remains readable at presentation size.

Then test the final deck on the computer and output equipment that will be used for the presentation. A successful playback on the author’s laptop does not demonstrate how the recipient’s setup behaves.

Keep the original media until the converted clip and deck have been accepted. Name the converted version clearly so a later revision does not accidentally restore the incompatible source. If conversion changes quality unacceptably, revisit the export settings or use a simpler approved presentation alternative instead of treating successful insertion as the only goal.

References: Microsoft: video insertion compatibility.