This rejection message is displayed when you buy P or ZP category stocks. These stocks are not listed on CDSL and cannot be delivered to your demat account.
P-category stocks are restricted from buying due to their illiquidity, infrequent trading, and concerns related to depository matters and high taxation. Zerodha (Depository participant) maintains all demat accounts with CDSL (Depository). Once you buy the shares, CDSL delivers them to your demat account. If CDSL does not list a security, Zerodha cannot credit the shares in your demat account, and buy orders are blocked.