Login issue

I am not able to obtain the access token after multiple attempts.
I am getting below error
"status": "error",
"message": "Invalid checksum",
"error_type": "TokenException"

Steps followed:
1) Obtained request token
2) Create SHA256 online by giving api_key, request_token,secret without space
3) Invoked https://api.kite.trade/session/token?api_key=mykeyvalue&request_token=requesttokenvalue&checksum=1F4770D9D7D9A5B0DFCF5FD266234EFB72E3D86265A376CD898A3C951C903DBE

Could you let me know what is wrong with this approach?
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