I am having the same issue with instagram, they have allowed me to have a Facebook shop which is running fine but Instagram has regretted me, I am surprised as they are both the same company.
They sent an email with a link to appeal but it doesn’t work and I don’t even know what the reason for the appeal would be, why don’t they tell you straight away what the reason for rejection is instead of leaving me guessing.
Hi Craig - Facebook Shop and Instagram Shop are different. I can help you get approved if you'd like. growmeow.com/instagram-shopping