Unable to connect to AWS RDS instance

I have set up a AWS RDS instance. I am using "end point" as hostname to establish the connection via MySQL workbench. But the connection is failing.

I am sitting behind a company firewall and as per online tools, port 3306, the port that I am using to for the connection is closed.

Can this be the reason why I am not being able to connect?

Yes, it would be.

To get to an RDS instance you need to have the instance in a security group that allows inbound access to port 3306 from whatever IP addresses you want to access it from, and your local access needs to allow port 3306 outbound to the RDS instance.