Currently no tweets are displaying for me, not even tweets from pages I saw Twitter posts on previously. This started happening... not sure exactly, but earlier today all tweets were displaying properly.
EDIT: Now they are displaying, but they were not for a good 15 minutes. *shrug*
Version 49.0.2623.112 m
Edit: Appears to be working in Microsoft Edge.
Oddly the posts leave a gap like they're trying to embed the tweet as opposed to just keeping the link.
Edit: Aaaand they're working again. Weird.
I've also seen this behavior on desktop Safari