Check to see if you are getting voltage to it
Set your multimeter to VDC connect the red ternimal of the multimeter to postive and its black lead to its negative terminal
see if it is getting a voltage
If your are not getting any voltage then check its fuse
If it is getting voltage then more then likely the fan itself is gone
If you want to do a teardown of the fan I found this
https://www.youtube.com/watch?v=9YIz2Z6-AZA