Once a deadline passes, you will no longer be able to open a saved draft that you were preparing for submission. The draft submission will appear in your Saved Drafts list as Expired.
For this reason, it is recommended to keep a copy of your draft entries in an offline form of documentation. Since it isn't possible to download an active saved draft from your account, you may want to copy and paste questions and answers from a saved draft into an offline document or take screenshots of your drafts.
Once a deadline has passed or a form has been closed for any other reason, Submittable cannot help you with it. Please contact the organization directly to ask if your draft can be reopened. Contact information can usually be found on an organization's website.