When I try to bring down the Achievements tab in Area 51, it's showing an error dialogue.
Strangely enough, the global inbox dropdown works just fine.
Could be connected to this issue.
Area 51 fetches all topbar dialogs from Q&A sites through a private API. Some refactoring was done in A51 code recently that replaced old-school
string.Format calls to construct the API URL with interpolated strings... a stray closing parenthesis snuck into the URL at that point, so naturally nothing worked.
The commit message said "HTTPS and area51.meta.stackexchange.com move", so I have to give this one to Shadow Wizard and blame SSL on the purest of technicalities. ;)