Connecting to RDS via MySQL Workbench difficulties

I'm currently attempting to set up a low-complexity site that includes access to a database. The current step I am stuck on is connecting to the RDS database via MySQL Workbench. I've attempted to set up my RDS and Workbench connection the simple way so that it should connect.
I've searched through a dozen or so pages like stackoverflow and various aws resources, to no avail. I followed the instructions on this one especially: https://stackoverflow.com/questions/28429493/how-to-connect-mysql-workbench-to-amazon-rds and also https://linuxhint.com/connect-aws-rds-mysql-workbench/ but it still won't connect.
My RDS is "publicly available: yes" The security group my RDS is part of has an "Inbound Rules" set up: IPv4, MYSQL/Aurora, port 3306, Source (my ip address).
In Workbench, I set up the connection the way that the top answer in my Stackoverflow link dictates.
The error message comes up "unable to connect to localhost" and recommends I check thinks like "is it running" "on port 3306" "do you have permission" and "is the password right" which, as far as I can tell, are all correct.
I could really use help with this, please.