Steps to reproduce:

1. Installed and configured Zabbix and successfully connected to Database
2. Completed initial configuration of Zabbix on Web Server UI
3. When logged into Web Server UI, Error on bottom of webpage shows "Zabbix Server is not running: the information displayed may not be current."
4. Checked zabbix_server.log and error shows up "1240:20181004:232619.957 [Z3001] connection to database 'zabbixdb' failed: [2003] Can't connect to MySQL server on 'remotehost.rds.amazonaws.com' (13)
5. From Zabbix Server cli, used "mysql -h 'remotehost.rds.amazonaws.com' -u zabbixuser -p" and confirmed I can connect to database successfully
6. created PHP script to connect to the same database via PHP and confirmed connection is successful.
7. Double-checked zabbix_server.conf and confirmed correct DB settings are defined
8. Double-checked zabbix.conf.php and confirmed correct DB and zabbix server settings are defined.
9. Disabled SELINUX entirely to rule out SELINUX blocking anything. Error persists
10. Went to Amazon RDS and EC2 security groups and opened up all traffic to rule out any network connectivity issues. Error persists

Most of my research indicates that SELINUX or Amazon Security groups to open traffic will resolve the issue, but none of these have helped. Weirdest thing is that I can connect to the DB just fine via Linux CLI and PHP. This issue is driving me insane. Please help!