When recording a Call and choosing a Detail Product, the corresponding Key Message does not appear in the Key Messages section.
The user's language does not match the Key Message's language.
Available Key Messages are those where the Language_vod field matches the user’s language or where Language_vod is blank on the Key Message.
Be sure that the user's language matches the language of the Key Message, or do not specify a language on the Key Message.
CRM Help Documentation: Using Key Messages on the Call Report