Agree grounds.
Here is the issue

At key on - the ground is OK enough to pass a few amps which can run the lights.

When you try the starter, the junction at the ground goes up in temp and in resistance.
You can't get enough AMPS to run the starter.
And trying the starter makes the connection even worse as it has heated up and can pass even less current.

Please clean the battery terminals with a circular wire brush.
Clean the grounds.

Make sure the braided ground strap from the driver's side or Cylinder #1 side
is there and goes from the head to the firewall.

 

It's not the ground, next?

 

Can it be a frozen starter, and can autozone test it? But that wouldn't explain why it won't come out of park.

 

I had a really shocking awakening...

My wife had just had our third child three months early. He came out in June instead of Oct. He was 1lb 15 oz. It was the next day, the outcome didn't look that great...but I needed to go home and get the family while he was still alive...I wanted everyone to meet him.

I go out to the Rover...turn the key and nothing. It wouldn't start. The lights and things worked like it should but nothing...

I then got out, started crying, breaking down in the parking lot.

Locked and unlocked the Rover...and got back in and it started.

I then ran home grabbed everyone and now Sawyer is 18lbs and doing good...

The problem?

I told my wife about the little incident in the parking lot, to which she says...

When someone messes with the doors and the Rover is locked it never starts unless you lock and unlock it first.

So she knows, and makes me remember it all time...its her way of digging at me.

 

Jesus, that's an intense story.

I guess because we have a child due in Oct it resonates with me.

I just remembered that one day I got in and it wouldn't start, and I thought it was a alarm issue. I messed with it for a while and it finally just cranked. It entirely possible that locking and unlocking might have been the solution.

 

Frozen starter is possible, but unlikely. You'd hear a click or see a power drain of some kind.

You're sure it's not immobilized? Is the alarm LED on the dash flashing?

 

After it wouldn't start I ripped out the aftermarket alarm brain box thinking it might be it.

 

Why would anyone need an aftermarket alarm on a Land Rover?

 

Was there when I bought it...

 

Where does this white wire go? What's left over after pulling the alarm.