Hank here from Shopify. Really great question!
The most likely reason that your SSL is still pending is due to what is known as domain propagation which can take up to 72 hours to update across servers worldwide, although it is normally resolved within a few hours.
Sometimes it has to do with how the DNS records are set up within your domain, and if there are multiple A records associated. You will need to ensure that only one A record is associated as this will have a direct effect with your SSL certificate. I will share a snippet from the guide below for ease of access!
If you are still experiencing the issue, can you share your store URL so that I can take a look at your domain and see if there are any issues with it?
All the best,