On some browsers users are unable to login. Users also don't get feedback. The Magento system just doesn't respond. Sometimes the login does work in incognito mode.
Some things I already checked
– formkeys are integrated in the forms
– "web/cookie/cookie_domain"
are for all storeviews set to null. – We run multiple storeviews eg; example.com/en/ , example.com/de/
I also tried modifying the cookie settings in the code as suggested on this url http://blog.chapagain.com.np/magento-admin-login-problem/ (however this article is related to the magento admin, where our problem is the frontend) but also that didn't work.
Best Answer
It can be a problem in your template. You need to include form key in following templates:
Source: http://www.webspeaks.in/2016/02/magento-1-9-2-cannot-create-account-on-frontend.html