Please set spindle as rotary spindle before rigid tapping

Rigid Tapping User:
Hello sir, we are using GSK980TD for regid tapping, there is alarm:
Please set spindle as rotary spindle before rigid tapping.
What does it mean? We are using frequency inverter for spindle, and the program is:
G99 M03 S300 T0101 G0 X0 Z3 G33 Z-20 F0.7 G0 X100 Z100
Is there any wrong of this program? Thank you.
CNCmakers Support:
The frequency inverter is not able to make rigid tapping, you need to use AC servo spindle motor and driver, and it must be set as rotary spindle mode.