Authorisation Endpoint failing with Wrong credentials.

We have been trying to use the Auth endpoint by passing the client id and secret that we recently generated for our Personio App.
But we have always received a Wrong Credentials error.
We also tried to run it using the Try It Out feature available on the Personio developer link https://developer.personio.de/reference/post_auth but received the same resposnse.

Also something which has been very strange is that the client id and secret of our app changed thrice without any modifications on the app from our side.

Would really appreciate if someone could guide us in what is the reason and how we could fix this.

For debugging purposes,
Our Client ID's that we passed to the API calls are

1: papi-9f6f5f02-405d-4906-826f-7f83bf93efae
2: papi-b13b294c-8f47-4475-8208-d200e84fcfcb

Received same response from both the client-id's. Note that these are ID's from the same App we created on Personio for our API integration.

Thanks,
Rishabh