Okay, I have been dealing with this for a month! You can NOT edit DNS settings with the .shopify url. However, I finally got a customer service agent on chat with Shopify that was able to help. You CAN do a metatag verification. This worked IMMEDIATELY and after a month, I got a message from Instagram saying I was now approved to shop!! Use this option instead of dns verification!
I unlinked shopify from instagram, then relinked it. Uninstalled the instagram app and reinstalled it, then followed the process to select a domain in Instagram, then in FB Business Manager add a domain and verify using a meta tag. I am no IT whizz but I managed to get through it after a couple of searches.