This may or may not be linked with the problem described in Reputation not appearing in Rep. Notification Queue - yet it is given silently (which is apparently site-wide, not just on Super User).
The site-wide activity page (
https://stackexchange.com/users/USER-NUMBER/USER-NAME?tab=activity) which shows a summary of one's activity across all Stack Exchange sites seems not to be being updated.
I'm having trouble uploading an example image (imgur is rejecting the request): you can get to the page by clicking the icon/reputation/badges element in the top menu, then the Network Profile link to the top-right and then selecting the Activity tab.
My page shows my last activity as 22 hours ago, although I have answered at least one question and made a number of comments since then.