Doesn't read RFID tags by RFID reader FX7400

i'm trying to read RFID tags by using FX7400 reader which connected to .Net MVC application. application connect to reader successfully and read each tag's tag id first time it seen by antenna. The issue is when tag seen by antenna second time, reader not identify tag. which means reader doesn't at least blink acknowledge indicator.

i used same application with this same devices once before. and it worked without any issues. it seems like enable or disable any configuration in reader. so i need help to identify it and fix it.