In most cases changes to the Liquid XML Objects generation settings or the XML Schema (XSD) will cause the code to be re-generated automatically. However if the schema is part of a schema set or automatic code re-generation is turned off then you will need to force re-generation manually.

Steps 

1. Select the .xsd or .xsds file in the 'Solution Explorer'.
2. Right click on it and select the 'Run Custom Tool' Menu item.

This will cause the code to be re-generated from the schema or schema set.