This problem doesn't exist exclusively on ios 7, it has been around for years. It happened to me as well, and I tried many methods, and what ended up working for me after hours of work was just to reinstall ios 7 and then using an old backup and waited for a few hours, and it just magically worked. If you google this problem you can find many solutions and I suggest you try all of those or as many as you can, and one of them is just to wait for 24-48 hours and see if it'll activate in time.