How many volts did you get?/
At the solenoid activation terminal not the battery cable .
Unfortunately the test light will only tell us that you have power, not how much.
If there is insufficient due to voltage drop in the circuit then the solenoid will not pull in.
Frequently it is necessary to upgrade the circuit to include a relay.
There needs to be the same voltage at that terminal as there is at the battery.
Most modern test lights will illuminate at 3v - 30v and not indicate any difference.
If you need a hand fitting a relay I can guide you through it.
The first thing to do is a little bypass to confirm the diagnoses.
Take a length of 6mm or thicker wire and attach it to the trigger terminal on the solenoid.
Make sure the car is in neutral with the key off.
Attach the other end to the positive terminal of the battery.
The starter should wind over.
Give this a try and let me know the results.
Then we will go through fitting a relay.
It's a common procedure.
Right I haven't heard how you got on so here is the relay wiring.
You will need a 40 amp relay and some 6mm wire.
You can get both at the local parts store.
You will need some push on terminals for the wires to connect to the relay.
Firstly mount the relay somewhere near the starter motor but not in the way. The relay will come with a mounting bracket and a self tapping screw will screw into the firewall of the car.
There are 4 terminals on the relay they are numbered on the relay 30, 87 , 86, and 85.
Take the trigger wire off the starter motor and connect it to terminal 86.
take a short piece of wire , crimp a terminal on one end and attach it to terminal 85 and the other end to a good earth point. I usually use the mounting screw for this. ( you will need a round eyed terminal for this.)
Connect a length of wire from terminal 87 to the trigger terminal on the starter - thats where you took the other wire off.
Measure a length of wire to run from the battery positive terminal to the relay.
Connect one end to terminal 30 on the relay and the other end to the positive terminal on the Battery.
You have now wired in a starter relay.
Turn the key and it should go.
6mm wire about 2 metres
4 push on terminals
2 round terminals (1 small 1 large)
1 40 amp relay.
Let me know if you need more help