first - please check in your sms whether any mobile activation code has come. if it has come, just enter the code and continue. if not, you can request for the verification code again. mobile verification code sms will come, just type your login id, pw and provide the verification code in the column provided and the normal booking can be done through irctc.
if you have provided any other mobile code, check in that number. verification of email id and mobile phone are being done now. hence without mobile ver. code, its a problem.