Cannot receive or send email with TWC POP3 account, account is locked

We really need to see the entire error message verbatim in order to be able to help properly. However, if it looks like this:

… it's most likely that you're accessing this same mailbox from another device, like a phone or tablet. There can only be one connection to a POP3 mailbox at once. If you are accessing the same account from a mobile device, and that device is using push mail, then it will monopolize the connection and not allow any other client - e.g. Windows Live Mail - to connect to the mailbox. Try disabling the account on your phone for a while to see if the problem goes away (this might take a day or two). If it does, reconfigure the account not to use push mail, but rather POP3 at a different interval from whatever Windows Live Mail is set up for.

You can't change the type of account (POP3 or IMAP) once it's set up in Windows Live Mail. If you'd like to try Spectrum IMAP, you'll have to set up a new account from scratch using the recommended settings. Once you've done so, you can drag any messages you want to keep (e.g. sent items) from the POP3 account's folders to the corresponding ones under the IMAP account. Once there's nothing left that's important in the POP3 account's folders, you can right-click on the account name and select Remove account.