Are you able to locate the reset button on your router? On most routers, it is located near the power outlet. If you can do a reset of your router, usually by holding down the reset button for about 10 seconds or so until all lights flash, then you can try using the default settings. Go to the router control web page, and try entering "admin" for the user name and leave the password field totally blank. If that does not work, try "admin" and "password" for the password.
OnePlus 5 review