I cannot find that option to "check"... Where is it located?
These what I see in the polylang settings...
The language is set from content
Posts, pages, categories and tags urls are not modified.
The language is set from the directory name in pretty permalinks
Example: http://www dot northernvision dot eu/en/my-post/
The language is set from the subdomain name in pretty permalinks
Example: http://en dot northernvision dot eu/my-post/
The language is set from different domains
Hide URL language information for default language
Remove /language/ in pretty permalinks
Example: http://www dot northernvision dot eu/en/
Keep /language/ in pretty permalinks
Example: http://www dot northernvision dot eu/language/en/