Language switcher not work

Hello, please need help. Language switcher not work (in the upper left corner), installed English and Russian.
If choose language, i get this: mysite.com/en/index.php?route=common/language/language and The page you requested cannot be found!
Previously, there were no such problems, no changes were made. I use SeoPro.
I checked the script on hoster server and local server, under local server everything works correctly.
Support of my hosting told, that no changes has been made.
Can you help me with this?
Thank you.

Please help, version of my Opencart is 2.0.3.1

Did you make sure, to have BOTH Language SEO-Fields, where they exist,
containing a valid and language-specific SEO-Name/Title ?
Ernie

Both languages are there. If manually switch the language in the browser's address bar, it will switch.
I get the error The page you requested cannot be found! anytime I try to pick a language and even going back to the default.
Thanks for the answer.

yoursite/en/index.php?route=common/language/language
would not work anyway, exept, if you use some kind of custom Mod,
changing the way, to select a language.
Ernie