This is Moira from the Social Care team at Shopify. Thanks for posting, and a very warm welcome to the Community!
On your mobile device, access Instagram then go to Settings > Business > Shopping > Website and you should be able to click on your new domain name or click “verify another website in catalog”. From previous experience, I was then able to tag products again. As a first step, make sure you have already verified your new domain on Facebook Business Manager and you shouldn’t have any issues. I suggest deleting your old domain name on Facebook Business Manager to avoid any confusion.
Let me know how you get on!
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