@safetynetweb check that the redirect_uri parameter is exactly the same in Acumatica and in your request

Thanks @Dmitrii Naumov 

I checked and confirmed yes they are identical but still getting same error 

Instead of using Hybird method which didn’t work for me after many tries not sure why, I implemented hte password method to get the refresh token, and then I used the refresh token to get access tokens for future uses

$req =  
'grant_type' => 'password',
'client_id' => $client_id,
'client_secret' => $client_secret,
'username' => $username,
'password' => $password,
'scope' => 'api offline_access'
];

//the above get the refresh token, then next I use it to get the access token

$req =  
	'grant_type' => 'refresh_token',
	'client_id' => $client_id,
	'client_secret' => $client_secret,
	'refresh_token' => $refreshToken
];

Thank you for sharing your solution with the community @safetynetweb!