Sometimes there are some language issues in ESS some ways to find where lies the error are shown following:
You have 6 steps to check when regarding language.
1) JCO is NOT maintained blank (Mantained blank is the ideal to get the browser language)
2) Iview property Forced language is wrongly maintained;
3) User has incorrect language settings;
4) Browser has incorrect language settings;
5) Particular language is not installed on portal;
6) Wrong customizing in IMG;
As a tip is good to know the following:
Clear the JCo language setting so it picks up the user's login language.
Then you will have to log into ECC with the language you want to
translate for and make the IMG Homepage settings in that language.
SAP Note 947081: Locales, languages, date and time formats in Web Dynpro