Like 260 million other websites, we use an SSL certificate from Let‘s Encrypt. On 30 September 2021, the old SSL root certificate used by Let‘s Encrypt expired, and they started using a new one. This new certificate is only included with iOS 10 and later, so devices running iOS 9 or earlier are unable to verify that our current SSL certificate is valid. So on these old devices Breviarium Meum displays an error and refuses to download data.

To get Breviarium Meum to work on a device running iOS 9 or earlier, you will need to install the new Let's Encrypt root certificate. Here is a direct link to the certificate.

If do not trust the direct link (as is wise for something as important as a root certificate), go to the Let’s Encrypt Chain of Trust page, scroll down to Root Certificates, and tap the "pem" link for the self-signed ISRG Root X1 certificate as indicated below:

Let‘s Encrypt root certificate download

Installing

When the iOS device downloads the certificate, it will recognize it as a configuration profile and open it in the Settings app. From here you just push Install, enter your passcode, push Install again, and push Install a third time on the dialog that pops up. The push Done, and Breviarum Meum will be working again. You will also be able to visit the numerous other websites that use SSL certificates issued by Let's Encrypt. In case that wasn't clear, here are pictures of the process on an iPad 2:
Certificate installation step 1
Certificate installation step 2
Certificate installation step 3
Certificate installation step 4
Certificate installation step 5