Performing a search with "Formula" works as expected. Search with "Query" fails. Printout attached to better document the problem.
Mathematica is still using the SOAP APIs (e.g. AsyncSimpleSearch). Turns out the SOAP APIs were retired nearly a year ago. New RESTful APIs have been available for the last 18 months. For authentication, the new APIs require an API key which is not compatible with the SOAP APIs. A SOAP security token, which the Royal Society of Chemistry no longer makes available, was required to authenticate the SOAP APIs. Searching based on "Query" does not work because it requires authentication. Searching based on "Formula" still works because it does not require authentication. Therefore, until Mathematica is updated to use the new APIs any of the Mathematica ChemSpider routines requiring authentication will not work.