TWRP loop on booting nokia 3?

i successfully installed twrp but on twrp reboot i selected system and now on opening nokia 3 it goes to twrp. Only twrp can be opened not the OS (normal boot) of nokia 3. I tried flashing stock rom of nokia 3 with sp flash tools but on starting or booting phone , it will not detect nokia 3 and red and yellow bars does not appear. so how to flash stock firmware when i am stuck boot looping in to Twrp. Any other way if possible please describe.