Since end of September: Mac devices show cert problem on my domain, but not other lets’encrypt encrypted domains

[ReinhardSchagerer]

Hi,

Mac devices (iphone etc.) show cert problem as a new problem after years of functioning perfectly since end of September on my domain, but not on other lets'encrypt encrypted domains.

I know the root cert was exchanged, so I compared the cert of https://shop.bbc.com/ with mine https://support.webboard.org and found out there is not much difference, my public cert is even the doubled bit size.

My domain is: https://support.webboard.org

Why are these errors only on my page when visiting with apple devices but not on other domains using letsencrypt? I already issued a new cert but it doesn't help.

Please also see https://community.letsencrypt.org/t/since-end-of-september-mac-devices-show-cert-problem-on-my-domain-but-not-other-letsencrypt-encrypted-domains/164047/2