The tracker is a factory fitted box that allows the car to be found if stolen, you should have some credit card sized black boxes with the car, that’s what they are for. It also has a relay to stop the car starting, it interrupts the start signal from the gearbox computer to the relays under the bonnet that engage the starter. Mine went wrong and stopped the car starting just like this, but it gave me the “go to dealer and spend loads of money” message.
To be honest, if there was a fault with most things, it would give that message, so there is something more fundamental at play.
In the box with the ignition relays you mentioned there is one called the “start enable relay”. I would pull this relay and test it and see if you get 12v to the coil when you turn the key.