The thumbnail cannot be displayed. After checking, it is found to be a permission problem. After setting the permissions of the userfiles folder to 775, the problem that the thumbnail is not displayed is solved.
But I still can't enter Admin, it may be a problem with permissions, but I don't know the permissions to modify which directory, please let me know, thank you.
In addition, I can make a Chinese language file, but every time I set the language, the old language file will change, So I have to rewrite the language file, which is very bad, please tell me how to do the language file will not be changed.