After installing, when I log-in it doesn't work

Hello all,

I have just installed a mutlisite version of wordpress with Btinami, amd I can see the home page of my site.

The problem is that I cannot log in to the administration part: when I enter my credentials it is like if it just refreshes but nothing happens (and there is no error message), it stays on the log-in page. I noticed though that when I put wrong credentials, I have an error message.

I tried to reset my password by clicking on “Lost Password”, it sent me then a link, but when I click on it I reach the log in page with this message: “Your password reset link appears to be invalid. Please request a new link below.”…

I case it helps, here are the access log generated each time I enter my username and password:

::1 - - [12/Jan/2016:00:47:58 +0100] "POST /wp-login.php HTTP/1.1" 302 -
::1 - - [12/Jan/2016:00:47:58 +0100] "GET /wp-admin/ HTTP/1.1" 302 -
::1 - - [12/Jan/2016:00:47:58 +0100] "GET /wp-login.php?redirect_to=http%3A%2F%2Flocalhost%2Fwp-admin%2F&reauth=1 HTTP/1.1" 200 1092
::1 - - [12/Jan/2016:00:47:59 +0100] "GET /favicon.ico HTTP/1.1" 200 -

Any idea what is wrong?
Thanks a lot.