You need to give us full network setup info.
What modem and broadband type do you have?
Is the modem also a router with wireless?
How is the TC connected to the modem?
What mode is the TC in, ie bridge or router?
How is wireless setup in the TC?
If you are prepared to just start over.. then just reset the TC to factory.. plug it into the computer with ethernet and do the setup again.
Give it all SMB type names.. this just means, short names with no spaces and pure alphanumeric.
Use WPA2 Personal security only with 10-20 character password. Pure alphanumeric mix of upper and lower case and numbers.. but not dictionary words.
Set fixed wireless channels.