For a candidate to be able to retake your test (i.e. submit another attempt after the most recent one), you can either re-invite the Candidates to the same Test (When you do so, a Candidate's Test status initializes to “Invited”).
Note: When Candidates try to access a Test for a reattempt, sometimes, a browser-level cache may disallow them from logging in to the Test. To overcome this issue, it is recommended that your Candidates access the Test link using a new browser window.
To re-invite candidates to a test, you can select one or more candidates from the Candidates tab in your test, and click on 'Re-invite Candidate', as shown below. For more information on re-inviting candidates, please read the full article here.
Note: When you re-invite a candidate, the most recent attempt by the candidate is archived. A candidate can be re-invited as many times as needed.