This is because the Sample Database contains only ENU repository data and seed data. You cannot launch the Mobile Web Client with the Sample Database in the non-ENU language.
In order to import Non-ENU Repository and Seed Data into the Siebel Sample Database, you need to run the samp.bat located in SIEBEL_CLIENT_ROOT\sample\UTF8, where SIEBEL_CLIENT_ROOT is the directory where you installed the Siebel client and the Sample Database.
Before running the samp.bat, make sure the SQL Anywhere database engine is running. Just start Sample Database in English, it will keep running even after you log out the application. But keeping the database engine running is needed.
The syntax for using the samp.bat batch file is as follows:
Example in my case is:
samp "C:\Siebel\8.1\Client_1" "SEAW Samp Db default instance" FRA
After running this batch, I can launch the French version Sample database now.
More information please refer to bookshelf:
or the document in support.oracle.com