If you attempting to call the Team Messaging API in sandbox, but are receiving the following error:

{
"errors": [{
"errorCode": "GLP-021",
"message": "This API requires the requester to have a Glip profile.
You might sign in to the application to create it."
}]
}

Then, that is an indication that your team messaging account may not have been fully setup yet. This rarely happens in production, but can happen in the Developer sandbox because sandbox accounts are setup using a unique process not used in production. The fix is to log into our [Team Messaging sandbox application][1]. As soon as you login for the first time, the setup process for your account will be completed successfully, and you will no longer receive the above error.

[1]: https://app.devtest.ringcentral.com/