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And you still cannot login? How about the extension number? If you login with a main company number, make sure the extension number is correct.

All numbers were updated along with the secret and the url. We have tested two different users and get the unauthorised error for both.

What is your app client id? And can you share the code where you implement login? Remember to remove sensitive information.

many thanks our client app id is: SH6M36tASyOYPuBuCpbi5Q

the implementation code can be downloaded from here (its php so I could not attach or paste in): https://we.tl/t-qyzarB0Hra

I cannot access the code. I found your app and I am so sure that either the app credentials or the user's credentials are incorrect.

I cannot ask you to confirm sensitive information here so either you submit a support ticket request. Or double-check the credentials.

I don't fully understand what you wrote earlier either "we are generating a token with production user credentials (and have tested on another user credentials) and app client id and client secret"

What did you mean by "have tested on another user?" When you login, do you use the main company number or the extension's direct phone number? Do you also use the extension number? If you can post the code where you implement login, I can check it for you. But remember to remove sensitive info such as password and client secret.