I have added a third language (Thai) as a package to my script (Zen Cart) and the database (id1624330_1). The flag is also displayed in the start page. In the admin area the language is neatly integrated and in the database it is also clearly recorded.
Nevertheless, if the language is called by pressing the flag, a "500" error message appears instead of the start window in Thai. I deleted the cache, helped nothing. I waited a night, helped nothing. A 500 error is a server problem, I can not make more. Can you because times times look why this error is displayed?