Epson Tm-T88v print issue

why does print job get into queue when i use port monitor on the printer port for an epson TMT88V receipt printer? I have installed epson standard windows driver, printer installed on the physical serial port, then i have installed port monitor to monitor data on serial port, Then after restarting the system when i gave print, print is not coming to printer, its stays in print queue. But when i stop the port monitor, give the print to printer and then start the port monitor and give the print, print properly coming to the printer. So unable to understand why TM-T88v wait for sample print without port monitor?