Hello aspirant,

You need to refresh the page and fill up again the necessary details and choice filling and check whether the choice locking is available or not. If it's there, then click it. And, if it's not, maybe there is some technical issue or the conducting board has not yet made the choice locking option available in the official website. Wait for some time till the choice locking option is made available. Else, if anything is not made up to your mark, then you must immediately contact the helpline desk of the conducting board of the respective official website.

Hope, it helps you.