Authention issue while getting token using Auth code ,3-legged oauth code flow error

Hi All,

We are using the 3-legged api flow mentioned in the below documentation.
REFERENCE URL: https://developers.ringcentral.com/guide/authentication/auth-code-flow

STEP 1: Login URL, where user is redirected to the ringcentral login page for authentication and concent.

https://platform.ringcentral.com/restapi/oauth/authorize?response_type=code&redirect_uri=<my_uri>&client_id=<client_id>&display=&prompt=

STEP 2: We are successfully receiving the code in response to our redirect URI specified. When we make a second request to receive the token we are getting the following error message.

*REQUEST URL:* https://platform.devtest.ringcentral.com/restapi/oauth/token

*REQUEST TYPE:* POST

*REQUEST HEADER*

"Accept"=> "application/json",
"Content-type"=>"application/x-www-form-urlencoded; charset=UTF-8",
"Content-Length"=>144,
"Authorization"=>"Basic BASE64CODE({CLIENTID}:{CLIENTSECRET})

*REQUEST BODY PARAMETERS*
"grant_type" => "authorization_code",
"code" => {RECEIVEDCODE},
"client_id" => {CLIENTID},
"redirect_uri" => {REDIRECTURL},

*RESPONSE WE ARE GETTING*

{
"error" : "invalid_grant",
"errors" : [ {
"errorCode" : "OAU-222",
"message" : "Account does not exist"
} ],
"error_description" : "Account does not exist"
}

Please let us know the solution to this.

Thanks in advance.