Situation when getting “Error 404 – page not found” on all pages in one language. In other language everything seems ok. So…

I allready try to:

•  “flush” permalinks. It does not help. If you save permalinks in current language, this language posts work, but other language not.
• changed language in the top wordpress settings bar and saved permalinks again. In changed language pages started working, but…. Now my main language articles (pages) not work…
• change permalink structure. It does not help.

If I change permalink structure to “default” (http://localhost/abc/?p=123) everything works. But I need the “pretty” permalink structure.

So I found solution in function.php I added this line

flush_rewrite_rules( false );

More about this can read here.