Final version cannot be uploaded

The "final upload" feature does not work, authors cannot upload their final version. Why?

Please note that authors can upload final versions for accepted contributions only (not for submissions with the status "rejected" and "on hold").
They can upload the files on the page "Your Submissions" for existing submissions only when they click on the link "Final Upload" (see image).

If the final upload link does not appear, please check the following options:

• Is the person the main author? As per default, co-authors have only read access to the submissions.
  (You can change that in the "Main Settings for Paper and Abstract Submission" via the option "Full Access to Submissions for Co-authors".)
• Have the global deadlines in "Phases and Deadlines" for the "Final Upload" phase been set correctly?
• Has the alternative deadline for the corresponding submission type / conference track been set correctly?
• Did you set the acceptance status for this submission?
  Final uploads are (normally) only enabled for accepted submissions.
• Is the final upload (still) enabled for the corresponding acceptance status?
  It is enabled as standard for all “accepted” statuses.
  You can change it on the page "Manage Acceptance Statuses": Activate the expert settings and go to the option "Enable Final Uploads".