You created a DB instance in RDS. You cannot connect to it. What should you do?
1. Make sure that it is "Available." It could have been turned off.
2. Click on the Instance and confirm the relevant Security Group allows you to connect to it.
3. Click on the Instance and search for "Publicly accessible". Make sure this is set to "Yes." If it is set to "No" you may have to take a snapshot of the instance and launch that snapshot with the "Publicly accessible" option.
4. If you are still having problems, try this set of directions. If there is a potential network problem, you may want to view this posting.