Access to public URL

I have been using the free tier of grafana cloud, connected to an AWS Timestream database. A public URL that I have provided to a few selected persons has worked well.
Now the public URL fails consistently with an error 401 (when reading https://<my_application> and will not show any data.
On the same laptop, I can open another browser, log into my grafana acccount, and then use the public URL on that browser. Possibly, this picks up an access token from the login.
No change has been made on my side - is anyone aware of changes made by grafana cloud? I have already updated the Timestream plugin.