In bcece my rank is 8807 and l was not in the first meritlist,so my resistration was failed,it shows the rollno is invailed.So what can I do
If your name isn't in the first list then wait for the second or third marit list you din't have to do separate registration for it but as you told your roll no. Is showing as invalid then contact the authorities ASAP but before that make sure you have done your document verification and other necessary details without any error.
Hope it helps