TL;DR Create a new app and re-apply for production.
When you change permissions for your application, you will need to re-apply for production access with the modified sandbox tests (similar to what you originally did to receive production access) and we will review in our weekly production access meeting on Thursdays at 12pm Pacific.
How do we re-apply for production access. The permissions are un-editable. Do we have to create a whole new app?
As per the link below, it's mentioned "
You have to clone the app and add new permissions. Then test your app in the sandbox to make sure it uses all the new and old permissions and meet the max error rate requirement."
Ref:- https://forums.developers.ringcentral.com/questions/1511/how-add-permission-after-completion-of-production.html
However, as per I know once your app is in production, you cannot change anything.
You need to ask the developer support team for any help by creating a support ticket. Once they added the permission with your request(not sure if they do.. most probably they don't) you need to test again for that permission you acquired.
The official recommendation is to create a new app, add proper permissions and graduate it. So in that case you need to go through again.