Apologies for the late reply,
Please not we have migrated to API_V2.
These issue may arise due to some reasons,
1.If the app_id passed is not correct,
2.If the app_type is not present (like -100, -101)
3.IF the Auth-code generation url is incorrect, the url will look like this """https://api.fyers.in/api/v2/generate-authcode42? client_id=SPXXXXE7-100& redirect_uri=https%3A%2F%2Fdev.fyers.in%2Fredirection%2Findex.html &response_type=code&state=sample_state&nonce=sample_nonce"""