Lastpass not accepting Webroot credentials

I never set up password management in WebRoot but noticed an email saying that tomorrow was the last day to 'upgrade' to LastPass.

Thinking this is something I *should* do, I logged into my WebRoot account, clicked on 'Manage Passwords' but the LastPass site rejects the email/password combination I entered -- "Invalid email or password!" -- even though it is exactly the same as just entered to access WebRoot and follows LastPass instructions: "Please log in using your Webroot username and password."

I searched this forum and apparently this is an long term, ongoing problem. I see Moderators making suggestions and people responding with variations on 'Nope. Doesn't work." Still haven't found a clear answer.

There is clearly a disconnect between WebRoot and LastPass. This does not inspire confidence. If YOU have gotten this to work, please advise how you did so.

Thanks in advance!