There are many things that can be going on.
1. The scooter needs the manual brake engaged in order to work as a safety feature.
2. The clicking that you hear when you press the throttle is the release of the brake which is normal.
3. The amp meter reading 0 is normal on a full charge. If you go to plug it in and the needle doesn’t move, wiggle or jump, then the charger is bad.
If the scooter can be pushed around in “free-wheel” mode then your scooter will not work (its a safety feature). You need to engage the manual brakes before turning it on. Then it will work assuming everything else is ok.