Ted here from Shopify, thanks for posting your query!
From what you have described, your domain's A Record is pointing correctly to the correct IP address, however, the CNAME needs to point to shops.myshopify.com. More info can be found here if you would like to take a look. It can take up to 48 hours for these changes to fully adjust and for the SSL certs to be issued.
If it has been beyond 48 hours, please update and clear your browser's cache or try an alternative device and view your store using the custom domain.
If you are still experiencing issues do please let me know and I'll take a closer look into this with you. Our support is always available here 24/7 as well if you would prefer a faster response.