the ADR1614 cannot output with Electronic load machine

Dear

       I'm using ADR1614 to a boost circuit,Vin=3.7-4.2V(Battery),vout=5V@2.4A(Max), when power for the Phone or PAD, the output is OK!  but if test the functions on Electronic load machine, whaterve the load current, 100mA, 500mA etc, the output is droped , even down to zero, like the output protect.

      L=6.8uH,Cout=22uF*2,Didoe is PMEDG4030ER.  the components of the part are all OK. why it cannot work normally with the E load? many thanks