The test might not be available due to any of the following reasons:
- The test link has expired. This means that the recruiter had set an expiry date for the test after which test could not be accessed by the candidates.
- The test might have a particular scheduled time. However, you might be trying to access it at the time that falls outside the scheduled time.
- The test owner might have deleted the test.
To resolve this problem, you can contact the recruiter and request for a new test invitation. HackerRank cannot reset the link without explicit communication from the concerned recruiter.