How to resize CentOS partition after increasing volume capacity?

Assuming you cannot start the instance, you should detach the root volume and attach it to another dummy/test instance. The idea is to increase the file system size manually. Once that is done, you can re-attach the volume to the original instance and start-up.

Please refer to this link for the file system size increase steps

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/recognize-expanded-volume-linux.html