Why is there is a missing interview stage in an Assignment?

Firstly, check the Pipeline's Settings to see if the interview stage has been created. Secondly, create a new Assignment because Pipeline changes are not reflected in Assignments or Recruitments that have already been created.

Why can't I find a seafarer whose profile is in the system?

Firstly, check both the Candidates and Seafarers pages. Secondly, remove the default status filter which is set to Active on the Seafarers page. If you still cannot find the seafarer, contact support.