You might not be able to pledge your holdings for a few reasons:
Not Available for Pledge: Only certain stocks, ETFs, and SGBs that are listed as 'Available to pledge' can be pledged.
Open Sell Orders: Stocks with open sell orders can't be pledged.
Stocks Not in Demat Account: Stocks you've bought today will be available for pledge after they are credited to your demat account, which takes one business day (T+1).
Existing Pledge Request: If you've already placed a pledge request, check its status before submitting a new one.
Note: You can only pledge holdings between 6 AM and 9 PM on market days.