The set of supported versions is unordered, which might you a different error message in different scenarios:
No map found for version V26. Only the following are available: [V251, V25, V23, V24, V231]
No map found for version V26. Only the following are available: [V231, V24, V25, V23, V251]
...
The error message is not going to show up anymore: if a structure library is not present, the HL7 message will be parsed into a GenericMessage object