We only use one refresh token. when the access token is expired then  we will hit the endpoint below to get a new access token

but as you can see, I have invalid_code error. could you please help what went wrong in here?

previously I can get the new access token just fine, but I don't know why this morning I get this invalid_code error.

I don't think I ever revoke the access token. I have  a connection in Zoho CRM that has the same scope when I create 'self client' . I think I revoke the connection but then I turn it on again. is refresh token API and connection are connected?

I am trying to fugure out the root cause so it will never happen again