Next step in diagnosis? Yaris 2005 wont start

First time posting on this stack-site so forgive if I do it wrong and please let me know how to improve my post.

I have a 2005 yarris that stopped at the lights a few months back and wouldn’t start again(starter wasnt turning over).

I thought maybe I had a flat battery so I got RACQ(the local car club / help folks) to come help me and they couldn’t get it to start with their battery so we got it towed back to my place.

I checked all the fuses none looked damaged so I removed the starter motor and tested it on another car battery. It seemed to spin up fine.

However when I connect the same battery to the car and attempt to start the engine the starter won’t turn over.

I think, but I’m not certain that I can hear the solenoid on the starter clicking when I turn the ignition.

I’m running out of ideas, I thought it was time to hit the internet in search of next steps.

What would the most common trouble shooting steps be in a situation like this?

I think my next step is to check the electrics going to the starter, so in that vein I’m going to search the web for a wiring diagram.

---

UPDATE 1

I have now checked every relay in the starting circuit and they all work fine.

I pulled apart the ignition think cleaned its contacts and checked against the spec I think they are all measuring correctly.

If I disconnect the signal cable from the starter and jump from the signal connection point on the starter to the power in it turns the starter on but the engine doesnt start.