Just to run through the obvious that most people forget to try first
a. F12 (or whatever it is on your computer) to turn on/off wi-fi.
Can you
log into the modem directly? Remember, Charter gives you a modem. They don't give you a wireless router unless you pay extra for it (~$6/mo) and it's always separate; most people supply their own wireless router which connects directly to the modem via ethernet cable.
Not connecting at the library has nothing to do with Charter.
b. Select hibernate/sleep from the Windows Start icon, rather than relying on pre-sets and simply closing the lid.