Sometimes SSL certificates that are issued by Certificate Authorities include intermediate/chain certificate files that reach their expiry date. This is not the same as when a main/server certificate purchased by your organization reaches its predetermined expiry date.
If the SSL certificate in use on your site contains an expired intermediate/chain certificate file, it may result in certain SSL errors to your site.
Additionally, SSL certificates cannot be installed on our platform if the intermediate/chain contains an expired file and attempting to do so will result in an error message. We have more information about that installation error here.
In order to resolve this, contact your SSL vendor/Certificate Authority and request an updated intermediate/chain certificate to be used along with your existing main/server certificate.
Once you have the updated intermediate/chain certificate file, re-install your existing main/server certificate with its associated private key with the new intermediate/certificate file for your respective environments within the Acquia Cloud Platform UI.
We have instructions on how to install SSL certificates here.