Updates: The issue has been resolved in Joplin Cloud, so if you had the "Ignore TLS certificate errors" option enabled, don't forget to switch it off as it is not secure. If you are self hosting and are having troubles with this bug, please give a try to the latest pre-release, which includes …

Fix for "Certificate has expired" error with Joplin Cloud and self-hosted sync targets

Topic		Replies	Views
Letsencrypt root CA certificate expiration Support	16	2648	1 October 2021
NextCloud / WebDAV Cert Error Support	24	5504	20 June 2020
Certificate Error since upgrading to 2.4.9 on Windows Support	2	946	3 November 2021
Certificate expired Support	7	568	4 March 2022
Joplin Server Syncing Failed - Cert Expired - HAProxy Support	2	1254	1 October 2021