Token security invalide

I have create a web site with grav but when i login in admin she say "Token security invalide"
What is the problem

If you're running the latest stable release of Grav and Admin, there is no known issue apart from this one

I have this problem on a fresh installation of the latest Grav Version (1.1.14).
Every time i click on the plugins menu i get the login screen and after login the message "invalid security token"