Hello aspirant!

Firstly, you have not mentioned which exaam are you talking about. Secondly, you have mentioned November 2019 in the question. I suppose, it is a typo and you mean to say 2020.

Now, assuming it is AIIMS institute, if RUC code generation option is not available, then it means  your application has not been accepted. Kindly check for any message or email from AIIMS which verifies that your application is accepted. If it is accepted, then check your application status. You can login using your credentials. Then there is an option for "generate unique code".

Now, however, new registrations are closed. So you cannot do basic registration once again.