I was able to resolve the problem for now by moving to LetsEncrypt as our AutoSSL provider.
Step 1 :
Install Lets Encrypt cpanel plugin
Run the following command in ssh : /usr/local/cpanel/scripts/install_lets_encrypt_autossl_provider
In WHM -> Manage AutoSSL -> Providers tab -> Select Lets Encrypt and click save.
Run AutoSSL For All Users (Alternatively you may just do it for the domain where ssl did not renew)
Thank you for this! I have no idea why suddenly my AutoSSL stopped working, but this fix worked.
I have only one question related to the authority of LetsEncrypt vs cPanel. Do you think that using a LetsEncrypt certificate for my subdomains vs. a cPanel certificate would impart anything negative to google or other search engines? I know this may seem like a silly question, but I've heard that the quality of your SSL certificate issuer is important, but then again, this could all be just marketing BS.