Time for a video showing us your field of view with the IVS rules and sampling of it tracking along with screenshots of the PTZ setting page that shows track ratio (or whatever it is called LOL).
So its two ivs set one square on almost whole area and tripline on the road begining but there is some bushes so maybe that why its take longer time to begin track the car. Its hard to read numberplate at night and on the day i have to stop in right frame but its long distance so i just use a digital zoom to read
I can have a look for you at your settings via TeamViewer if you wish. What I would say is RESET the camera back to Factory fresh a FULL RESET so the IP goes back to 192.168.1.108 then set your IP what you want and pop me a message when set to fresh.