Can't connect to AWS postsql RDS

I'm trying to stand up a Dev database for a web app. I have setup the Dev database using a snapshot from the current prod server. I'm currently trying to restore the dev server's DB from a .dmp file I have via:

psql --host=blahblahblahblah.us-east-1.rds.amazonaws.com --port=5432 --username=postgres --password --dbname <dbname> -f backup.s

Which gives me the error:

psql: error: connection to server at "awseb-e-gjem7uperk-stack-awsebrdsdatabase-1hzzq9r4a74c.cg7ksxih0nnz.us-east-1.rds.amazonaws.com" (3.225.21.170), port 5432 failed: Operation timed out Is the server running on that host and accepting TCP/IP connections?

I believe I have followed all the recommended steps to debug.

1. Check that the host name used is the DB instance endpoint and that the port number used is correct - yes, they are correct. I copied directly from the RDS Connectivity & security page.

2. Make sure that the DB instance's public accessibility is set to Yes

3. Make sure that the user connecting to the database has CONNECT access to it - (THIS ONE I'M NOT SURE ABOUT How can I do this if I can't connect?)

4. Check that the security group assigned to the DB instance has rules to allow access - I have access to everybody. I know it's not best practice, but I'm trying to get it to work right now

Any ideas what is causing me to not connect?

Check out my post on stackoverflow for additional context/images: https://stackoverflow.com/questions/76553853/cant-connect-to-aws-postsql-rds