Hi Dennis my sincere apologies for the delayed response and Stephen thanks for continuing this thread! There can only be a single Lucid account associated with an email address which means that you will not be able to change the current email address of your account to a new address if that new address is already associated with a separate account whether paid or free. There are several options here:
1. Delete the other separate account that currently is associated with the email address you want to use on your main account. That will free up that email address for use and you will be able to change it in the account settings of your main account.
2. Change the email associated with the other separate account to a third alternative email. This will free up that email address for use and you will be able to change it in the account settings of your main account.
I hope this helps! Please let me know if you have questions about either of these options.