In magento 2.2
Multiple store views on one store
If you change the language twice in a store this system won't redirect you back to the right store. Instead it gives a server error with the message: Requested store is not found
Steps to reproduce
Solved! Go to Solution.
Are you getting hte same result using the Luma Theme?
It seems there are several reports related with this problem.
Maybe you should check at http://github.com/magento/magento2/issues/ to add more information to existing issues or create a new one there. (Since this error seems to be a bug)