'There Was a Problem Playing This Video': How to Fix It

getting ‘there was a problem playing this video’ across a few different contexts. saw it on youtube, then on an embedded player on another site, and also when trying to play a local file.

it’s not every video. some play fine. the ones that fail don’t seem to have anything obvious in common.

browser is up to date. tried clearing cache. didn’t fix it.

what’s the actual diagnostic approach here? i want to understand whether this is a browser issue, a codec issue, a network issue, or something specific to those video files. different causes would mean different fixes and i’d rather not try everything randomly.