Take a look at link below
Do check if your DP Id is in this list as banks have multiple DP id and not all of them are available for SPEED-e. Best way is to ask your broker if they offer speed-e for your DP id. My guess is if your demat is linked to your online trading with POA then SPEED-e is not available. SPEED-e is just an alternative to paper delivery instruction slips used in offline trading.
Check the FAQ on speed-e https://eservices.nsdl.com/SecureWeb/Faqs.html