I had this problem and the solution isnt very obvious
It has happened on 2 e-frames that i have had.
The trigger selonide has proberable come loose or shifted.
Take the trigger frame off and open it up. Stick a screwdriver to the 1 side of the selonide and make sure its pushed completly to the 1 side. Then make sure the worm screw is in tight which is located at the top of the frame pointing down onto the selonoid, using some threadlock is a good idea.
If that doesnt work then its likely to be the battery, in both of my e-frames only duracel ultra will cut it. cheaper batterys wouldnt work
You might also have problems with recharganle batterys as they tend to be a bit weak.
If you still have a problem putting a bit of oil on the sear can also help.