[Q]unknown usb device after using mtk droid tools topic

i root my canvas a1 using twrp by opening bootloder when i use mtk droid tools and click on root button after few seconds it show device removed and my device disconnected andand mtk droid tools having close after then i remove usb put it again in my phone but it show that unknown usb device then i do turbleshooting and recover my pc and restart it and also reboot phone also and it connect to the pc and i again use mtk droid tool and click on root the same problem again happen but now after recovering pc and rebooting phone the problem is same my phone still so unknown usb device .....
what i do anyone please help me.....