Nick here from Shopify. Great question!
Can I ask when it was that you tagged your products on Instagram? The reason I ask is that it can take some time for the products to be approved once they have been tagged. You can see more about this in Shopify's help guide for setting up the Instagram sales channel here.
This is something which is out of Shopify's control also and could be worth reaching out to Instagram directly for as per the message above. You can see the Instagram Help Centre here.
Hope this helps and looking forward to hearing from you!
All the best, Nick