Here's how your setup "should" work.
The Cable Modem is what brings in Internet Service into the house. If you plug into that Cable Modem, boom -- you have internet.
Now, plugin the Wireless Switch. The Wireless switch does nothing more than extend the signal from the Cable Modem to both the Wireless network and the physical switch (if you plug directly into the wireless switch with a network cable). Obviously you want to connect to the wireless signal so that's obvious.
What should be happening then is when you connect to the wireless switch (via WIFI / Wireless) it should pass your connection to the Cable Modem which will then give you an IP address and other important information like DNS and a Gateway etc...
What could be a problem your having is
1 - Wireless Switch is broken2 - Wireless Switch is misconfigured
Now being that it was working and now it isn't.... that tells me you have a hardware issue, not a configuration issue so you need to get a tech onsite to swap out some hardware.
However, if you want to troubleshoot. If it was me, I would login to your wireless switch and make sure you disable DHCP. This will prevent you from getting an IP address from the Wireless Switch vs. the Cable Modem. Now, reboot everything including your computer and try again. You should get an IP address now from the Cable Modem and be golden.
Hope that helps...