Greetings,
There are different log in pages for sign in depending on whether you are a legacy TWC or legacy Charter customer. To my knowledge, this forum only supports legacy TWC customers (Not legacy Charter or legacy Brighthouse Networks at this time.)
Can you log in through this site?:
https://www.spectrum.net/login/?ReferringPartner=TWC&loggedOut=true
If so, bookmark it, if not what is the error message that you are getting. What browser(s) are you using?
Satch