After receiving this comment, I discovered that there's a reputation requirement for realtime notification updates: Using my Sock Puppet, I checked that 90 reputation is not sufficient.
- What is the (reputation) requirement for realtime updates using Web Sockets?
- What's the motivation for this requirement (including the rep. threshold)?
EDIT: I did not test properly. 90 rep worked fine.
2055992
(the SE ID (I probably used the Stack Overflow user ID).