Cal here from Shopify, thanks for reaching out to us.
Domain transfers can take up to a week to be processed successfully, so it wouldn't be unusual for it not to be completed after days.
Have you followed this guide for transferring your domain into Shopify? There are some vital steps that you must follow for the successful transfer of the domain to Shopify. If you have followed this guide carefully, I would suggest reaching out to your domain host to make sure the transfer was initiated from their end.
Let me know how it goes!