If a 404 error appears my menu change the language. Any reasons for this problem? Thank you!

Hello,

When you encounter a 404 error, it means that the URL entered does not exist in JoomSEF's database, so it doesn't know what language it should display, so unless you have saving language to cookie enabled, it just displays the default language.

Best regards,
ARTIO Support Team

Changing "language to cookie" to yes doesn´t solve the problem.
My Language integration is set to "different domains"!

Hm, that's strange. Thanks for the report, we'll check this.

Best regards,
ARTIO Support Team

I try the same setting for "language to cookie" ("yes") in another project with just one domain and Language integration is set to "include in pasth". The same problem exist.

I found another hint for you. If I change the setting "Main language" to "none" the same problem exist, but only the button-name change the language. The link of the button stays in the chosen language.
Example:

Button "Imprint" change to the german "Impressum", but the link ist still "/imprint" and not "/impressum"!