Can't Get Access Token

POST https://emr.vlabnigeria.org/apis/default/fhir/oauth2/default/token
My Header
Content-Type:application/x-www-form-urlencoded
Authorization:Basic cVo0NUpKMmZHdHRDSE5PdEdJT3dTQXhLQmZka1VYaW0tTjJGVmYtblpTbzo0SnNJel93NzdxcU1mdUtDZXRMUXRCWDMyWl84WmZiSnNTZDItUmVJVWtJOXJiUHhySzNQcGdqVkNhamJnZndONlFybDVmMkhsWkpPWFdMX3VjN0oyZw==

My Body

grant_type: authorization_code
client_id:xxxx
redirect_uri:http://localhost:8000/home
code: xxxxxx

Response
{

"error": "access_denied",

"error_description": "The resource owner or authorization server denied the request.",

"hint": "The JWT string must have two dots",

"message": "The resource owner or authorization server denied the request."

}

Please someone help me out