The symptom is that none of the new uploads are appearing.

It also (apparently) stopped me from receiving "All Activity" notifications from github repos.
I had configured github to email those notifications to my cpan.org address and they stopped arriving 3 or 4 days ago.
Earlier today I altered that email setting on github to instead specify my gmail.com address, and email notifications started arriving shortly thereafter.

No sign of the missed notifications, of course - but that's not important.

Update: Aristotle Pagaltzis has subsequently raised the possibility that I might instead have simply been hit (belatedly) by:
https://log.perl.org/2024/02/cpanorg-email-deliverability-issues.html
I don't know ... to me, that seems a bit too coincidental, but I can't rule it out.

Cheers,
Rob