Can't connect to admin

When I try to connect to admin, the page refreshes and… nothing, my login info are still there and I could do that over and over… can’t connect.

It’s not a bad password, as my lockout plugin (3 attempts) don’t lock me out nor mention a wrong passord… only refreshes page !

I have tried to deactivate all plugin (rename all directories) with no succes.

I have tried to deactivate the theme (still no success)

I have tried to upload old WP-ADMIN and WP-includes… gave a blank page : no success.

Any ideas ???