The SSL certificate (of Let's Encrypt) of one of our websites (https://edu.electrosuisse.ch) expired yesterday morning. It has renewed itself using the services of Let's Encrypt several days ago. Yet the browsers that already got the old certificate seem still to be using the expired one without showing any warnings. [Shift] + Reload does not fix this.
If you open a browser window in 'private mode' then the new one is being used. But this does not update the cert of the regular browser window, neither.
(Also online SSL check tools show the new SSL certificate.)
Same behaviour for Firefox as with Chrome/Edge Chromium.
So there seems not to be any problem, but does anybody know why browsers do behave like this?
(Unfortunately search engines just deliver results for problems with expired certs etc.)
Info displayed in regular browser window
Not Before: Fri, 27 Nov 2020 04:43:23 GMT
Not After: Thu, 25 Feb 2021 04:43:23 GMT
Info displayed in private browser window
Not Before: Tue, 26 Jan 2021 07:47:26 GMT
Not After: Mon, 26 Apr 2021 07:47:26 GMT