I´m facing the same error.
Apache logs contains:
[Tue Apr 24 11:00:56.406620 2018] [:error] [pid 24270] [client 192.168.1.51:10650] PHP Fatal error: Uncaught IPS\\Db\\Exception: Unknown column 'in_editor' in 'field list' in /var/www/ipb/system/Db/Db.php:501\nStack trace:\n#0 /var/www/ipb/system/Db/Db.php(838): IPS\\_Db->preparedQuery('/*IPS\\\\Session\\\\S...', Array)\n#1 /var/www/ipb/system/Session/Store/Database.php(77): IPS\\_Db->replace('core_sessions', Array, true)\n#2 /var/www/ipb/system/Session/Front.php(283): IPS\\Session\\Store\\_Database->updateSession(Array)\n#3 [internal function]: IPS\\Session\\_Front->write('vo02n1ithl5i96b...', '')\n#4 [internal function]: session_write_close()\n#5 {main}\n thrown in /var/www/ipb/system/Db/Db.php on line 501
[Tue Apr 24 11:01:00.772933 2018] [:error] [pid 15826] [client 192.168.1.51:10655] PHP Fatal error: Uncaught IPS\\Db\\Exception: Unknown column 'session_cookie_key' in 'field list' in /var/www/ipb/system/Db/Db.php:501\nStack trace:\n#0 /var/www/ipb/system/Db/Db.php(838): IPS\\_Db->preparedQuery('/*IPS\\\\Session\\\\_...', Array)\n#1 /var/www/ipb/system/Session/Admin.php(123): IPS\\_Db->replace('core_sys_cp_ses...', Array)\n#2 [internal function]: IPS\\Session\\_Admin->write('87hc8esn6uppl9l...', 'forcedWrite|i:1...')\n#3 [internal function]: session_write_close()\n#4 {main}\n thrown in /var/www/ipb/system/Db/Db.php on line 501, referer: http://webserver/ipb/
[Tue Apr 24 11:01:01.110661 2018] [:error] [pid 24268] [client 192.168.1.51:10656] PHP Fatal error: Uncaught IPS\\Db\\Exception: Unknown column 'session_cookie_key' in 'field list' in /var/www/ipb/system/Db/Db.php:501\nStack trace:\n#0 /var/www/ipb/system/Db/Db.php(838): IPS\\_Db->preparedQuery('/*IPS\\\\Session\\\\_...', Array)\n#1 /var/www/ipb/system/Session/Admin.php(123): IPS\\_Db->replace('core_sys_cp_ses...', Array)\n#2 [internal function]: IPS\\Session\\_Admin->write('87hc8esn6uppl9l...', 'forcedWrite|i:1...')\n#3 [internal function]: session_write_close()\n#4 {main}\n thrown in /var/www/ipb/system/Db/Db.php on line 501, referer: http://webserver/ipb/
Did you manage to solve it?
Thanks