Self-Client oAuth invalid_client

Self-Client oAuth invalid_client

Hi, I'm developing a client that works with Symfony Console (PHP + cURL) for my employer.
I've 2 accounts, a real one from the company and a personal (empty) one for testing purposes.

I set a Self-Client ID/Secret on both accounts. I've been retrieving data successfully, oAuth was working fine until a couple weeks ago that stopped working on the real account. The test account (this one I'm posting) still retrieving the oAuth token right.
I've created a new Self-Client ID/Secret but the problem persist.
I checked all I've at hand to see if there's some lock on the account, but everything seems fine.
How can I trace were is the issue?

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