After your lead will not continue to turn as deals, it will move into failed leads on the archive tab. Maybe in the future, you will have a better chance to process these leads. But, if the chance is coming. You can unarchive your lead and use it again as you needed.
First, go to the archive tab, and click the lead that you wish to unarchive. Then, you will see the detail lead. On the lead info, click the 'Unarchive' button. And, you will be prompted to confirm the unarchive request, click ‘Yes‘ to proceed unarchive the lead or you can click ‘No‘ to return to the detail lead.
Then, you will see a notification success and your lead will move into the Leads tab.