Can't log in ALIM Web

Hello !

I'm configuring ALIM now, already set up the server, communities, storages etc. all according to implementation guide. Got 1 additional user created in eB Director not to mention the admin, but when I set up the Web part my users can't log in receiving the following error message : 

Does anyone know what's causing this ? I guess this is something coming out of IIS, but I'm not sure