Why do I get a message “cannot verify atp.powernetco.com”

It would almost seem as though there is a profile associated with the app. Check Settings>General and look for a profile with that name on it. If you find one, delete it. Otherwise, you may need to contact that app developer to determine how to get rid of it.

What are you doing when you see this message?

Seems like this is some type of information site. Have you tried clearing your Browsing History and website data in Safari Settings? Maybe a website that you visited?