As per the new instruction:
If your Aadhaar card application status is showing as "Rejected" or "Processing Not Possible Due to Technical reasons" then it is advised to re-enroll for Aadhaar card and complete the entire process to get a new Aadhaar card.
In case your Aadhaar card online status shows "Not Found" and you have applied before April 1st 2012 then also it is advised to re-enroll Aadhaar card again.
In case of people applied after April 1st 2012 and if status shows "In Process" then you have to wait for one more month and then check the status. If no progress then contact concerned department or authorities.
In case your Aadhaar card is issued but you have not received the card physically then you can visit the UIDAI website and download it directly.