input these tags in your code, it will provide better logging in the vuser log, and will tell you what it is doing. I would place them around the submit data area.
lr_set_debug_message(LR_MSG_CLASS_EXTENDED_LOG | LR_MSG_CLASS_RESULT_DATA | LR_MSG_CLASS_PARAMETERS | LR_MSG_CLASS_FULL_TRACE,LR_SWITCH_ON);
lr_set_debug_message(LR_MSG_CLASS_EXTENDED_LOG | LR_MSG_CLASS_RESULT_DATA | LR_MSG_CLASS_PARAMETERS | LR_MSG_CLASS_FULL_TRACE,LR_SWITCH_OFF);