Private Instance | Agents not picking work

We are using WebPageTest with EC2 auto-started agents. My agent is properly started, the wpt-driver starts and is able to reach the server but agent never shows up under /install or /getLocations.php (hence not performing any test tasks).

So far I have checked:

Locations are okay, I am using only the default ec2_locations that comes with webpagetest, didn’t add any additional location.
Userdata for instance is correct, ec2.log doesn’t report any errors.
I tried both with and without “location_key” in settings.ini.
I have scheduled tests for the eu-west-1,eu-west-1-linux location that are waiting in front of the queue
ec2=1, ec2_locations=1, ec_initialized=1 are set in settings.ini
Double checked IAM keys settings in settings.ini.
Please help in pointing us to the right direction for troubleshooting.