I am having the same issue for months now. Can not connect my Shopify shop after installing Pinterest app. The catalog is now showing up. Pinterest name : thehomemind
Hi @theHOMEmind and welcome to the PBC!
Please, disconnect your Shopify app and Pinterest account by going to Your profile > Edit Profile > Security on Pinterest and clicking the Revoke Access button. After that, uninstall the app and install it again. This will reconnect everything once more.
I hope this helps. Let me know if I can help you further!