Zoho Invoice API- Customer Search - not finding?

Zoho Invoice API- Customer Search - not finding?

I've been using the customer search in Invoice API successfully with some text in the Notes field, but now I need to search by Customer Name - as the docs suggest I can. However, I'm not getting a match. The name does include spaces and a hyphen if this is a problem - ie. "My Customer Name - State". The name I send is an exact match for the name in Zoho (case, trimmed) but still no joy.

Ideas?