Unable to authenticate with Shibboleth

I tried restarting service (seafile, apache2 and shibboleth in all possible combinations), rebooting server and nothing helped. Currently I’m back to fastcgi because there’s quite a few people using seafile. However, I’ve kept configurations:

apache2:

RewriteEngine On
ProxyPreserveHost On

<Location /media>
    ProxyPass !
    Require all granted
</Location>

# seafile
ProxyPass /seafhttp http://127.0.0.1:8082
ProxyPassReverse /seafhttp http://127.0.0.1:8082
RewriteRule ^/seafhttp - [QSA,L]

# seahub
SetEnvIf Authorization "(.*)" HTTP_AUTHORIZATION=$1
ProxyPass / http://127.0.0.1:8000/
ProxyPassReverse / http://127.0.0.1:8000/

<Location /Shibboleth.sso>
    SetHandler shib
    AuthType shibboleth
    ShibRequestSetting requireSession 1
    ShibRequestSetting applicationId default
    require shib-session
</Location>

<Location /api2>
    AuthType None
    Require all granted
    Allow from all
    satisfy any
</Location>

<Location /shib-login>
    AuthType shibboleth
    ShibRequestSetting requireSession true
    ShibUseHeaders On
    Require valid-user
    ShibUseHeaders On
</Location>

seahub_settings.py:

EXTRA_AUTHENTICATION_BACKENDS = (
    'shibboleth.backends.ShibbolethRemoteUserBackend',
)

EXTRA_MIDDLEWARE_CLASSES = (
    'shibboleth.middleware.ShibbolethRemoteUserMiddleware',
)

SHIBBOLETH_ATTRIBUTE_MAP = {
    "HTTP_EPPN": (True, "username"),
}
#SHIBBOLETH_USER_HEADER = 'HTTP_REMOTE_USER'

ENABLE_SHIB_LOGIN = True
SITE_ROOT = '/'
SITE_TITLE = 'Seafile'
ENABLE_SIGNUP =  True

CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
        'LOCATION': '127.0.0.1:11211',
    }
}

SESSION_COOKIE_AGE = 60 * 60 * 8
SESSION_EXPIRE_AT_BROWSER_CLOSE = True
ENABLE_REPO_HISTORY_SETTING = True

USE_PDFJS = True
FILE_PREVIEW_MAX_SIZE = 50 * 1024 * 1024

CLOUD_MODE = False
ENABLE_GLOBAL_ADDRESSBOOK = True