2005 fiesta engine won't start.

Hi all. First off, this is my nephew's car I'm trying to fix and also my first time on here so apologies if this topic has already been covered (I did search but couldn't find anything related). The car battery is new, car key works when used manually and central locking works (rcl hasn't worked for quite a while though). Lights come up on the dash as normal but when turning fully to start the engine nothing happens, not even a sound. However, the immobiliser light was flashing and it seems that the fuse was also blown. My nephew changed the fuse and the light stopped flashing but everything else remains the same; ie. the car still won't start. Has anyone else had this issue? Many thanks in advance for your help.