If the verification is not passed, first check that the prism is absolutely clean before a standard liquid is applied. Make sure the standard liquids are in good condition and not past their expiration date. Also, inspect the prism surface, checking that it is flat and shiny without any scratches, digs or deposition on it.
Repeat the verification procedure. If the verification still fails, print out the verification report, send the data to helpdesk@vaisala.com or your nearest representative, and wait for further instructions.