Internationalization Bundle Issues with Custom Function Plugin

Hi guys,

I've built a custom function plugin which I have managed to deploy to one of our development environments successfully. The function is not appearing in /design despite including the function internationalization in the bundle. 

I'm seeing the following errors:

Expression evaluation error at function fn!getpvdetailsbyprocessmodeluuid: Error evaluating function fn!getpvdetailsbyprocessmodeluuid : The function 'getpvdetailsbyprocessmodeluuid' is unavailable.

...and in application-server.log:

2017-06-26 10:58:33,173 [ajp-/0.0.0.0:8009-2] ERROR com.appiancorp.util.BundleUtils - Cannot retrieve the value for key "function.getprocessmodeldetailsbyuuid.description" from the bundle.
2017-06-26 10:58:33,174 [ajp-/0.0.0.0:8009-2] ERROR com.appiancorp.util.BundleUtils - Cannot retrieve the value for key "function.getprocessmodeldetailsbyuuid.param.processModelUUIDOrId.description" from the bundle.

I've added a screenshot below of where the internationalization files sit in the package, and the content of one of the files is below.

function.getpvdetailsbyprocessmodeluuid.description=Returns an array of the PV names and types, e.g. "Name - Text"
function.getpvdetailsbyprocessmodeluuid.param.processModelUUIDOrId.description=UUID or ID of the process model

Can anyone tell me what I'm missing please?