How do you authenticate? Is the user under your production account? Trust the error message and check your user login credentials. Double check by login https://service.ringcentral.com. If you can login the service web, you should be able to login your app with the same credentials.

I'm using credentials from https://developers.ringcentral.com/ under Production Environment section. This is private app.

After login from https://service.ringcentral.com I got this message.

so my app is in production now . I use live credentials as following:

RINGCENTRAL_ID=xxxxxxxxxxyBSTB7w

RINGCENTRAL_SECRET=xxxxxxxxxxxxxxxxxxxx

RINGCENTRAL_URL=https://platform.ringcentral.com

RINGCENTRAL_USERNAME="xxxxxxxxx4735"

RINGCENTRAL_PASSWORD="xxxxxxxxxxxx"

RINGCENTRAL_EXTENSION="101"

maybe i have a wrong MVP premium account linked to my app?

can you please confirm the credentials

That is the case. Your app is created under your free-tier sandbox account. With such an account, you can only make public apps and allow all RingCentral users using your app.

The SendFax app is a private app, and it is a password flow app, which means that you cannot login the app with any user credentials under other accounts than your own account. But as this is a free-tier account, it is not associated with your MVP premium account.

You have to login the sandbox associated with your MVP premium account, create a new app, test and graduate it. Then you can login with any user under your MVP premium account.

we did upgrate to MVP Premioum. I spend a week on the phone with customer support to do it.

I have submitted the live MVP premium account number twice for this app.

what else can i do?

That is your free account. Stop using this. Login developers.ringcentral.com with a user under your MVP premium account (should work with the super admin user). Feel free to add more users as a developer to the dev portal.

You can submit a support ticket to get further support too.