No start - Starter doesn't engage

[tcheb]

The previous starter was fairly new but I replaced it with a brand new one to eliminate the possibility it broke prematurely.

The starter motor does not engage and does not spin.

[reelizmpro]

I'd be looking at the starter solenoid and the connections. Sometimes the fragile wiring breaks when you remove/install. Typically new starters, come with new solenoids though. So does the starter motor spin at all?

[tcheb]

I went through a lot of previous posts on no start conditions but the vast majority is about no fuel or no spark conditions. Mine is different.

When I turn the key, I can hear the click and the fuel pump activate but the starter does not engage. The issue started a couple of months ago, then resolved itself after a few days. Then a few days later the car refused to start again and the car has been sitting for a month and won't start anymore.

What I eliminated so far:
- it's not the ignition switch - I tried jumping the connectors in the diagnostic port and same thing happens
- it's not the starter - I replaced the starter and it didn't help
- it's not the battery - I connected it to an external jump starter and same thing

What else could it be???