When a user tries to use the "log in" page, it currently only works if they have a paid or "permanent free" account. But if the user doesn't have an active account (either paid or "permanent free") and does have a previously activated trial, then it should just use that.
To be clear, users can still "log in" to free trials using the extpay.openTrialPage() page. When they "log in", their user's trialStartedAt property becomes populated with the first time they activated a trial with that email address.