OP, is the lever saggy? Meaning no resistance when you pull the lever?
Not sure if you're aware, but the bonnet release cable is in two parts. The lever in the footwell pulls the cable at one end of a mechanism in a little junction box that's attached to the bodywork, in front of the washer bottle and behind the headlight. This then pulls on another cable that goes to the bonnet catch.
If the junction box becomes detached from the bodywork (mine was), then the internal mechanism won't work and the bonnet won't release. If the lever in the cabin is like pulling fresh air, you may want to check the above.