LanguageCode is invalid...

Error:

LanguageCode "{0}" is invalid for selected contact.

Explanation:

In the import file for the price list, a language code (LanguageCode) is specified for the language in which the price list is listed. Only languages that are set for the relation are valid. This error message means that a language code has been selected that is not set for the relation.

Solution:

Have the language code set for the relation or adjust the language code in the import file.