Maybe the ameter is connected in parallel to short-circuit.
It is not connected at all ( one or both probes would be open).
Or, the circuit is not powered.
The ameter is broken.
You didn’t connect the probes to the current input of the ameter. You should notice that in case of using multi-meter the ameter-function is working with different input-port than the voltmeter-function.
The ameter is set to measure DC current while the current in the circuit is AC.
You set the ameter to measure high current while measuring low current. Change the scope of the ameter step-by-step from higher set to lower.
Or simply, the current is zero.