we had today a new issue that the SSL Certificate from Let’s Encrypt wasn’t trusted by some browsers of our clients.
They are not happy, because they are loosing customers due to that and are blaming.
It’s not for all customers, that there is a problem.
Is there another Root Certificate issue on your side? Could you please check this and get back to me or @sebbler ?
If the cert install went fine then usually this happens because of DNS caching issue. When I run into this issue ( happens every now and then), I browse it from my phone with Wi-Fi turned off and mobile data turned on.