Hello, and sorry to hear about the problem you're experiencing!
The Toshiba C55 has a wireless card inside manufactured by Atheros, and it's give a lot of problems to a lot of people. The problem could be one of a few things, but let's rule them out one-by-one.
First thing to check is whether the device's software driver has gone nuts on you. Try this:
Right-click Computer (or This PC), and select Manage.
In the window that pops up, look for Device Manager on the left side, and click it. This will display (on the right half of the window) all of the various hardware devices built into your laptop.
Look for the Network Adapters category. If there's a minus beside it, see if there's anything listed underneath it and displaying a yellow exclamation mark. If there is, right-click it and choose to uninstall, then reboot your computer.
If there is a plus symbol next to Network Adapter, click it. You should find at least two devices listed underneath. One should be called Atheros (or give another indication it is your wireless network card). Right-click it, choose to uninstall, and reboot your computer.
After your computer reboots, Windows will re-detect and the device you uninstalled, and attempt to reinstall it automatically. Assuming this succeeds -- it should -- wireless access may be restored. If not, post back and we'll continue to the next step!