Alexa smart home skill lambda is throwing a LWA error - alexa

Question

I am developing alexa smart home skill. As part account linking i am getting AcceptGrant. I am getting below error,When i am getting access_token and refresh_token by using authorization code which i get as part of AcceptGrant request. Something i was missed. Same code is working for another skill. Could you please tell me what i missed?
ERROR Invoke Error {
"message": "Request failed with status code 400",
"name": "Error",
"stack": "Error: Request failed with status code 400\n at createError (/var/task/node_modules/axios/lib/core/createError.js:16:15)\n at settle (/var/task/node_modules/axios/lib/core/settle.js:17:12)\n at IncomingMessage.handleStreamEnd (/var/task/node_modules/axios/lib/adapters/http.js:293:11)\n at IncomingMessage.emit (events.js:412:35)\n at endReadableNT (internal/streams/readable.js:1334:12)\n at processTicksAndRejections (internal/process/task_queues.js:82:21)",
"config": {
"transitional": {
"silentJSONParsing": true,
"forcedJSONParsing": true,
"clarifyTimeoutError": false
},
"transformRequest": [
null
],
"transformResponse": [
null
],
"timeout": 1000,
"xsrfCookieName": "XSRF-TOKEN",
"xsrfHeaderName": "X-XSRF-TOKEN",
"maxContentLength": -1,
"maxBodyLength": -1,
"headers": {
"Accept": "application/json, text/plain, */*",
"Content-Type": "application/x-www-form-urlencoded;charset=UTF-8",
"User-Agent": "axios/0.24.0",
"Content-Length": 206
},
"method": "post",
"url": "https://api.amazon.com/auth/o2/token",
"data": "grant_type=authorization_code&code=RHmcOGELgCJeAHZUDtJm&client_id=amzn1.application-oa2-client.2e90a623fe5343baa8d201d038dd8666&client_secret=47cc11f1a945dde6d9844cf33ff2962fe064703c5a2ad5d651dbc29af31b539d"
},
"status": 400
}
Code
getTokensWithAuthCode(authCode) {
const body = querystring.stringify({
grant_type: 'authorization_code',
code: authCode,
client_id: ALEXA_CLIENT_ID,
client_secret: ALEXA_CLIENT_SECRET
});
return this.amazonTokenPost(body);
},
amazonTokenPost(body) {
return axios.post('https://api.amazon.com/auth/o2/token', body, {
headers: { 'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8' },
timeout: 1000
});
}