Julie here from Shopify Support.
Thanks for sharing this video. Typically, looping issues like these are browser-related. It looks like you're using Safari; I have seen similar issues occur with Safari, so can you please try again using Google Chrome? If you don't have Chrome, you can install it for free here.
It's also a good idea to clear your cache and perhaps try again using a different device or internet connection altogether. Sometimes these simple steps can do the trick!
If you're still experiencing the same issue after following the above steps and trying again in Chrome, then you'll just need to reach out to the app developers directly. In fact, the Pinterest developers have a dedicated email address specifically for Shopify merchants who are using their app, and you can access it directly under the Support section on their app page in the Shopify App Store.
Let me know how that goes!
Thanks for following up, @bilbordlorenzi.
The next thing I recommend doing is trying again using a different device and internet connection altogether. For example, if you're using a WiFi connection on a computer, try again using cellular data on your mobile device.
If the problem persists, then you'll just need to contact Pinterest's app support team directly. As mentioned above, their contact information can be found under the Support section of their app page. Since this issue seems to be isolated to their app, they'll be the best to assist.
Best of luck!