Why is there a red X next to my wireless network bars?

I'm having an error where I couldn't open my wireless networks to select a network, but after reading online and going to services to check if something's enabled and on the right setting, I clicked something and my wireless network icon turned grey w/ a red X.

It looks like this:

EDIT:
I'm still connected to my Wi-Fi network but it shows that icon instead of the full white bars.

After turning Wi-Fi off and back on, it still didn't work. But, after a restart, it worked and I can see my wireless networks.