@Mary44 This happens from time to time, it's some kind of software glitch. In my case, I stopped receiving text alerts, which is is my preferred method. I reported it, and it took about a month and a half for the alerts to start back up.
You can try going into your account page and checking to make sure the email option for notifications is still checked. If it is, try turning it off for a little while and then on again, that might reset it. Otherwise, you'll just have to report it to customer service and hope it gets sorted out soon.