See person on playback but no event triggered
Must be a vampire.
Seriously, person recognition isn’t a mature tech. Expect misses.
There is so little information in your posting that there are many, many possibilities.
Do you have the current firmware? Is person detection enabled? Is motion detection enabled, with a valid detection zone? Was the person 2-20 feet from the camera? Etc, etc. Read this document for more info about person detection: