The resume button is used when an advertiser has paused a campaign, and then wants to restart (or resume) it.
If you find that your account has been slowed (showing double gold asterisks), then analyze why this has happened, make appropriate changes, then click the 'Restore full delivery' button. As noted recently in this forum, you may need to log out, then log back in to see the double stars go away.
Also, please be aware that hitting the 'Restore full delivery' button will not restore a disabled keyword (with one red asterisk) to active status. One must first delete the disabled keyword, then re-enter it, hopefully with a more targeted ad, or in its own Ad Group.