Hello,

If the option is not available then they haven't kept that reservation category. You can write a mail to the board regarding the same. they will help you what to do next.

In some cases OBC reservation is not considered. It depends on the official board and they can only help you out as the form page is developed by their team.

They will surely give a way if there is any wrong else inform you why the option is not there.

Hope it helps!