If you are getting this error it usually means you are using Production on Cashfree Test server or Test credentials on Production credentials on Test. To fix this do the following:
Go to page where you get API credentials: https://merchant.cashfree.com/merchant/pg#api-key
Ensure that you get the appropriate set of credentials (Test or Production). Also ensure that there are no typos in the appId/secretKey
Ensure that in your integration type you are selecting the correct server (test or production) of Cashfree.