Why Won't My Photos Show on the Map?
A photo only appears on a map if it carries GPS coordinates. Here is why yours lost them and how to put them back.
Map views read GPS coordinates stored inside the photo. No coordinates, no pin. Most photo apps quietly show an empty map rather than telling you why.
Google Takeout is the usual reason. It moves the location out of the photo and into the .json file beside it. Social apps are another: WhatsApp, Facebook and Instagram strip GPS before sending, on purpose, for privacy.
If the .json files are still there, the coordinates can go back. Takeout JSON Metadata Fixer writes them into each photo, and your map fills up again. Everything happens on your machine, so your locations are never uploaded.