Laravel Queue Broken in Production

I've been working my way through a Laravel 8->9 upgrade (with the help of Shift.) After some initial troubleshooting with changed ENV variable names, I was able to get jobs added to SQS queues just fine. Locally, it works great. But on my dev and staging servers, the queues do not run. When I attempt to run php artisan queue:listen, it just sits there as if there is nothing in the queue. However, if I check the queue size in a tinker session (i.e. \Queue::size('public_dev');) it properly reports the queue size (which I can confirm on the AWS SQS dashboard.) The artisan queue:listen command works fine in my local environment with the same ENV file/credentials (save for the URL and DB.)

There are no errors in the logs.

Anyone have any ideas about what could be going on?

Here's a screenshot illustrating what I'm encountering:

EDIT: The plot thickens. I switched over to the database driver. Same thing! Jobs will just sit in the queue but not get processed. So at least it's not an AWS access issue.