Double check the fuse you put in is good, then check the socket you are plugging into is also working by trying another electrical device in the same socket.
Then you need to check that power is running to the trimmer to eliminate a possible broken wire in the cable. This would be best done by using a voltage detector pen - they cost £10 and well worth owning.
Next you will need to open up the machine and check that there is power running to the motor from the switch, also done with a voltage detector pen.
The results of these tests will identify the problem.