You cannot buy stocks on Kite if they are in the Graded Surveillance Measure (GSM) stage 2 or higher. These stocks require an Additional Surveillance Deposit (ASD) of 50% or more of your trade value. The exchange blocks this ASD margin for at least 2 months, even after you sell the stocks.
As part of Zerodha's policy, these restrictions apply only to your fresh buy purchases on Kite. You can still sell the stocks from your holding if you hold Graded Surveillance Measure (GSM) stage 2 or higher stocks in your account. If you want to purchase these stocks, you can contact Zerodha by creating a ticket.
To learn more about GSM, see What does GSM mean?