fmt messages will recognize some key's but others not

Question

So I'm working with fmt messages. But some of the keys that I am using aren't being recognized. Some key's work but other don't. This is the first time I'm using this. And I'm tottaly stumped. What am I doing wrong?

EDIT!

Ok I fixed it. Deleting and recreating all properties files fixed it magically. I still have no idea why he was giving me this error.

for example on the same page this will work:

<li><a  href="GameController?action=Home"><fmt:message key="home"/></a></li>

but this won't:

<p><fmt:message key="developers"/></p>

this is de properties file:

games.titel=Games    
home=Home          
prijs=Price      
game=game       
editGame=Edit Game        
naam=Name       
kiesDeveloper=Choose a developer        
addDeveloper=Add Developer           
developer=developer        
developers=Developers          
logIn=Log In
about=About          
editDeveloper=Edit Developer          
kiesGame=Choose a game         
voegGameAanDatabaseToe=Add a game to the Database          
voegDeveloperAanDatabaseToe=Add a developer to the Database       
addingGame=Adding a game                                                         

Answer 1

Ok I fixed it. Deleting and recreating all properties files fixed it magically. I still have no idea why he was giving me this error.