As a basic steps, please try hard restarting your console. Do you have any issues with other online games? What system are you on?
It might be worth checking that you have the right ports open: http://help.ea.com/en/article/ufc-ports-info/
I have the exact same issue since release, I've tried everything to included opening the recommended ports. I really need this fixed, this is pretty ridiculous.
Some of you did not link their GamerTag/PSN ID to their Origin account.
If you have changed your email address associated to your GamerTag/PSN ID, you may also experience this issue.
Directions for adding your PSN or Xbox Live ID to your EA Account can be found here.
If the issue persists, in your posts, please mention the exact error message + the platform you are playing on.