Dear aspirant, as you are saying you opted caste as OBC when you applied for the January mains but now you can't get your OBC certificate due to some issues.

First of all, have you applied for the April mains and if not then you must be knowing that you can apply for the April mains as a registered candidate only because if you apply as a fresh candidate and you have given the January mains then your form will be rejected.

Try to contact NTA officials regarding this query. Go to the Contact page from homepage. Contact on the first three no.(s) given on that page.

Good Luck.