Hi Ajay!

Try logging in using yor Registration Number and Password of your old registered account. Click on Modify Registration and try to change what you want.

I guess you might have entered your Matriculation Certificate Roll No. in your previous Registration, and when you typed the same again in new Registration, it shows Existing User.

So, kindly check by loggin in through your old account and try what I have said! Any queries, feel free to ask!

Hope this is helpful!

All the best!