Hello @traceystewartva,
Welcome to the LastPass Community!
I apologize for the inconvenience this is causing you. It's possible that the email was used to create an old account that maybe is no longer in use. For security you cannot share in the public community the email you want to use but I am sure that might be the case. Try making a delete account process for that email account so you can use it to change the email associated with your account. You can find the steps here: I do not know my master password – how do Idelete my account?
Kind Regards,
Alejandra
LastPass Support