The return value from the twain entry point (nCRet) is zero (TWRC_SUCCESS) when the call has been successful. A return value above zero means failure: check the twain status to know what happened.
You should change “if (nCRet)” into “if (!nCRet)” for your code to be OK.
And you’ll discover that the call has gone wrong, but you think it was OK, and the parameter list that you read is not the real one.
Good luck with twain. Alvise.