What does the error "RMS:Blocked for SM nse_cm MIS broker- ZERODHA block type: ALL" mean?

RMS:Blocked for SM nse_cm MIS broker- ZERODHA block type: ALL

MIS orders are blocked for SM group stocks, & thus the order was rejected & the above error was displayed.

The list of stocks on which MIS is allowed can be seen in the Margin Calculator.