For example, the correct answer does not appear in the list of available options, or where the problem statement is not precise enough to solve in an unambiguous manner.
There is no human I can talk to and ask clarifying questions to resolve the ambiguity because, you know, it is a HackerRank test!
After going through these experiences, I have decided that HackerRank test is just not worth the time. As a rule, I decline any request to take a HackerRank test citing my reasons as politely as possible. Surprisingly, more often than not, the recruiter is happy to setup a telephone round where I can talk to an actual human.