This Xbox account does not have permission to use this feature

Do you have a gold subscription?

Access to the online is usually run by the developer, not xbox live. More than likely your ea account I believe with fifa has to be reactivated with some permissions or there is an update. Log on from your computer to ea and update permissions and account
information

So I am going to ask a few questions that seem basic but knowing the answers will help us with understanding possible solutions to your issue.

First off is your Xbox Live subscription still active? If you run out of Xbox Live Gold time then you become Silver again and can't play online.

Second, did you buy Fifa 15 or did someone else buy it and you're on the same console as them? If someone else bought Fifa 15 and the Xbox you're on is their home Xbox then you can play their games, but if they changed their home Xbox you'll lose access
to all of their games, even if the game is still installed on your Xbox.

Your answers will help give me and others an idea of what we could be looking at and what advice to offer in order to help you.

Thank you for your fast comments!

Ill try all of them and see if any of them causes the trouble!

Do you have a gold subscription?

There was a free gold weekend this past weekend which would have allowed you to play for a few days without one.