What specific My Cloud device do you have?
Is it an OS3 (v4.x or v2.x firmware) or OS5 (v5.x firmware) My Cloud?
Have you tried restarting the My Cloud?
Have you checked the local network router to see if it is blocking internet access to the My Cloud?
Do you have Shares on the My Cloud configured for remote/cloud access?
What other troubleshooting steps have you tried?