500 Internal Server error : Unable to login after installation

[root@vps ~]# date +%z
+0400
[root@vps ~]#
[root@vps ~]# /usr/local/psa/bin/sw-engine-pleskrun -r 'date_default_timezone_set(@date_default_timezone_get()); echo(date(DATE_RFC2822)."\n");' ; date ; mysql -uadmin -p`cat /etc/psa/.psa.shadow` -Dpsa -e "select NOW()"
Sun, 18 Oct 2015 20:35:26 +0300
Sun Oct 18 21:35:26 MSD 2015
+---------------------+
| NOW() |
+---------------------+
| 2015-10-18 21:35:26 |
+---------------------+


[root@vps ~]# tail -17 /usr/local/psa/admin/logs/panel.log
1: cmd_loginup.php:135
createSessionCommon(integer '1', string 'admin', boolean true, string '111.93.159.50', NULL null, NULL null)
2: cmd_loginup.php:278
createSessionAdmin(string 'admin', string '******', boolean false, NULL null, boolean true, boolean true)
3: cmd_loginup.php:89
createSession(string 'root', string '******', boolean false, boolean false)
4: login_up.php3:45
[18-Oct-2015 20:24:34 Europe/Moscow] Session_Exception: Session expired
file: /usr/local/psa/admin/plib/Session.php
line: 410
code: 0
trace: #0 /usr/local/psa/admin/plib/cmd_loginup.php(135): Session->init()
#1 /usr/local/psa/admin/plib/cmd_loginup.php(278): createSessionCommon(1, 'admin', true, '111.93.159.50', NULL, NULL)
#2 /usr/local/psa/admin/plib/cmd_loginup.php(89): createSessionAdmin('admin', '$etd3v~H1', false, NULL, true, true)
#3 /usr/local/psa/admin/htdocs/login_up.php3(45): createSession('root', '$etd3v~H1', false, false)