For Shopping campaigns, you need to make sure that the language of your product data is the same as the language on your landing page.
This also applies to target countries supporting multiple languages such as Canada (supported languages: English & French). It means you can't submit your product data in English and show your landing page in French.
Some languages can only be used in one country (e.g. Swedish in Sweden or Turkish in Turkey) while other languages are available in multiple countries (e.g. Portuguese in Portugal or Brazil).
You can find the current list of languages that are available for Google Shopping here.