PeopleSoft: Default log-in page in local language, and localized numeric system

We've a client in Germany. So, when the users  there click on the hyperlink to open the PeopleSoft application the default log-in language for the application is German.

But one fine day, after upgrading the Internet Explorer, all the users were seeing the default log-in language as English; Although the language for the browser was German.
On the top of it, the system was not taking the comma as decimal separator but a dot.
That is when user was entering the amount 52,23 in the numeric field and tab out, it was being formatted to 5223.00 !

But after giving it a closer look, found that default language selected in the browser setting was 

 

Whereas it should be 

 

Because as per the PeopleBooks: 

• Web browsers enable users to specify a list of preferred languages for web content. PeopleTools uses the first language listed in the browser's preferred language list to determine the default language of the PeopleSoft signon page. If the user’s preferred language is not available, the default sign-in screen is displayed in U.S. English (en-US).
• For PeopleTools to display the sign-in page in the user’s preferred language as determined from browser settings, the language codes used by the browser are mapped to PeopleSoft three-letter language codes. The PeopleSoft system reads the PSLANGUAGES table to perform this mapping.