Consider sending a quick email to Shopify's support, and they'll look into the account.
Contact page link: https://help.shopify.com/en/questions#/contact/email
Thanks for reaching out.
I appreciate the context that you have shared. If you have recently connected your third-party domain to your Shopify store, the domain should automatically have the SSL certificate approved within 24 hours. Since you have noticed that the SSL is still showing with a pending status. I would suggest attempting to remove the subdomain and re-adding it back to the domain in question.
Based on the screenshot that you have shared, you can select Manage to see the subdomain that may be connected. Once you remove the subdomain, that may allow the SSL to be approved. With that being said, you can add the subdomain back to the store at any time.
Let me know if that does the trick, looking forward to your reply.
Happy to help out where I can! Feel more than welcome to reply back on the thread if you need any more assistance.
Have a wonderful day!