Since a few days, if you create a droplet from a snapshot that was (yum) updated, you will not be able to access that droplet via Terminal (ssh: connect to host ...** port 22: Operation timed out). You will be able to access only from the DO console.

Test this:
1- create a droplet with Centos 7.3
2- yum update the droplet
3- poweroff and make a snapshot
4- create a new droplet using that snapshot
5- try to access via ssh (Terminal / Putty)

You will not be able to login that new droplet. When typing ssh root@newdropletip, the password prompt will never appear (you will get a "ssh: connect to host ...** port 22: Operation timed out"