Check behind the parking brake pedal, there is a little plastic cam thing (big tech word) that has to be perfectly aligned to engage with the brake pedal arm. There is no adjustment to the cable itself, just that little cam thing can get misaligned with the pedal itself...and you just need to bend the arm to re-align it. Always make sure you always press the pedal so it goes straight on to that cam thing, do not jam the pedal down at an angle.
You can also spray it with some WD40 to clean off some of the dust and grime that may be preventing it from locking.
Cutch 88YJ