After I add all the information for a new subscription and click the button with the label "Submit for Review", the button itself turning red and show a sign of (i),
there is no extra information of the error, but on the browser console I can see the error:
POST https://appstoreconnect.apple.com/iris/v1/subscriptionSubmissions 409 (Conflict)
Submit for Review Error
Hello there, thank you for reaching out. This might be because your account holder has not accepted a pending agreement. Can you please verify that and try creating your app, subcritptfion or IAP again? Please see more information about agreements here.