How to customize log in text (private plugin)


I am using the private plugin, but I cant change the log in text. I edited the private.yaml file, but the default log in text is still displayed. The private.yaml file is read, since I changed the password, but somehow the log in text cannot be edited. You can have a look at my site:

Does anybody of you know how to change the log in text?

Thanks in advance for your answers.