Script not logging into Web Application

I have a script that is logging into an ESS Portal using Loadrunner 11.00. Using web_reg_find function it appears that even though the script replay shows as passed the script is not actually logging into the portal (web_reg_find_ function returns no value). I am using Web - HTTP/HTML protocol with HTML based script. The script does pass when replayed so all correlations appear to be in place.