After OBAS upgrade to 4.5.5-31 version it is not possible to login via nginx reverse proxy server anymore. Nginx reverse proxy server was used to protect access via IP-Access Lists and GeoIP validation.
New implementation of security (including Cross-Site Request Forgery) protection.
To find more information about new feature follow the link to documentation:
To disable a new implementation of security protection:
Add the following string to the end of /etc/hspc/hspc.conf :
SKIP_CHECK_HTTP_REFERER = 1
#service hspcd restart