Hi! Yes, you need to update the redirect URI in the app registration in the Azure portal. The redirect URI in your app registration needs to match exactly what you have in the app website on instagram (or in your code if applicable).
You can't register an instagram for myapp1.com and generate the url for mysite2.com. It must match a URL registered with the API key. Make sure there aren't any extra slashes or mismatches between http and https.
Some good examples here:
https://learn.microsoft.com/en-us/azure/app-service/configure-authentication-provider-facebook
https://learn.microsoft.com/en-us/azure/active-directory-b2c/identity-provider-facebook