For Derivative activation you need to activate the NSE_FNO section under myaccounts page with an ITR/Holding statement/Bank Statement. If that is already done and still it says client level not allowed then contact the support they will activate it for you.

Ankit Singh
Option Writing & Investments
Please contact the support regarding this issue then! And if possible, please do update me what the solution is. I'm seeing so many similar questions these days. Vanshika Singh