Works for me Try clearing cookies and log in again.
Thanks. No luck on that approach, but incognito window working fine. I'll update when I find the culprit (probably some extension or other) in case others have the same problem.
In case anyone has the same problem, it was a Chrome extension - Instant Multilingual PDF/HTML/TXT Translator - that had suddenly started breaking sites (PH was the first, but others soon followed). I'm probably fairly niche in running that extension, however