Good afternoon, and welcome to the forum.
Admin and sky are the correct login details.
If it is not accepting these, it is possible that at some point a user has created their own unique userid detail.
If you do not know that new userid, you could try resetting to factory defaults........ switch off computer, hold in the reset button on the rear of the router ( recessed in a little hole near the power input..use a blunt instrument to do the job ) for five seconds or so. Then reboot the computer, and you should be back to be able to use the default log in details.