Default location of docker-compose is /usr/local/bin/docker-compose but root does not contain path /usr/local/bin.
You can check is by following command:
[root@ip-172-31-40-117 ~]# echo $PATH
/sbin:/bin:/usr/sbin:/usr/bin:/opt/aws/bin
[ec2-user@ip-172-31-40-117 ~]$ echo $PATH
/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:
/opt/aws/bin:/home/ec2-user/.local/bin:/home/ec2-user/bin
You can add path for root, but it may not be a good way.(https://unix.stackexchange.com/questions/115129/why-does-root-not-have-usr-local-in-path)
[ec2-user@ip-172-31-40-117 ~]$ sudo su
[root@ip-172-31-40-117 ec2-user]# cd
[root@ip-172-31-40-117 ~]# vi .bash_profile
edit like this
export PATH=/usr/local/bin:$PATH
[root@ip-172-31-40-117 ~]# source .bash_profile
Or you can install docker-compose other path.