I am having the exact same issue, tried disconnecting and reconnecting, changing from business to personal and back, and I have had no luck. I have also looked all over google and there seems to be no answers? I have a tshirt company and I don't know why instagram would have denied us. we have been accepted previously on a different account.
No one can help with this matter as much as you try, beg, or hope. You are out of luck! Shopify should stop misleading small business owners with the promise of being able to sell on Instagram (according to the ads they are currently running on Instagram, Feb 2019). It's a deceptive business practice, pure and simple. Is shopify or IG to blame? Probably both. Unfortunately, I migrated away from a competitor that I was satisfied with because I wanted to take my business to the next level and sell on instagram. I spent a month setting up, customizing, and curating my shop, only to find that I cannot do what I wanted to do- what I have paid good money and time to do- and that is sell on instagram. Like the shopify ad said I could do.
My shop is within every guideline to sell: handmade porcelain jewelry from the states, plain and simple, family friendly for all ages, no sex or violence. I have already spent hours combing through all of IG/FB/Shopify terms of service and guidelines, chatting with friends who have IG approved shops, looking into advice about "maybe your tagging is wrong" or "make sure your categories are correct", etc. I've done everything humanly possible- spent hours tied up with shopify support, trying tutorials, having a FB business page, uploading my catalog, etc, only to be denied by Instagram with no option for review. Shopify gurus are unable to help me, saying that it's out of shopify's hands and it is instagram's fault, leaving me with an IG contact page and an alternative to use an app that doesn't do what I pay for shopify to do. IG doesn't have any contact information except for an email address that I have sent many messages to and have received no reply. In short- there is no way to contact IG. I have even tried to go the FB route. There is no way to contact Facebook.
Small business owners, please beware: using Shopify to sell on Instagram is not in your hands. So don't make the same mistake I did and waste tons of time and money. Tell your friends.