No E-mails flowing out of WordPress

Hello! I have a peculiar problem, where there are no e-mails flowing out of my self-installed WordPress instance (https://awsnewbies.com). I’m pretty sure it was working a few weeks ago, but when I am testing today, no e-mails are sent out.
I installed an e-mail logger, and while the e-mails are being created (as forms, comments, purchase receipts, etc.), all of them are not delivered with this error: Could not instantiate mail function.

Some background info:
It’s a self hosted WordPress instance, hosted on AWS EC2. I used the Bitnami AMI. The e-mails were flowing fine few weeks ago, but hadn’t checked it out since then.
I checked most of my plug ins and they seem fine (and I have same plug ins in other instances of wordpress and they work fine).
I have: Akismet, Display Posts Shortcode, Easy Digital Downloads, Google Nalytics for WordPress by MonsterInsights, Jetpack, Mailchimp, Table of Contents Plus, Yoast SEO. I’ve tried deactivating one by one and they didn’t seem impacted.
I’ve tried multiple e-mail addresses and none send.

Wondering if I need to adjust my security group on my EC2 instance to allow some e-mail protocol to flow through? I tried SMTP and SMTPS but didn’t seem to help.

If anyone has any idea, it would be very helpful! Thank you!

The page I need help with: [log in to see the link]