When sending an email, AI Email (AIE) checks that the lead is not receiving an email identical to a previous email. If the lead has received the same email previously, the AI email agent reports an error and cancels the conversation. This is a safety feature to prevent accidental spamming of a lead.
Currently, there is no expiry on this requirement; once a lead has been sent an email your AI email agent will never send same email again to that lead.
If you need to reach out to the lead again, either update the messaging, or add some context-specific merge tags to your messaging to vary the email content.