not able to get access_token after login. Invalid `checksum`

hi,
i'm following Kite Connect API Javascript client v4

var KiteConnect = require('kiteconnect').KiteConnect;
var kc = new KiteConnect({
api_key: API_KEY,
});

kc.generateSession(request_token, api_secret)
.then(function (response) {
console.log(response);
})
.catch(function (err) {
console.log(err);
});

this is the response i'm getting .what could be the possible reason ? i,m passing updated request_token everytime .
{status: "error", message: "Invalid `checksum`.", data: null, error_type: "TokenException"}


thanks