If you are having a trouble in accessing your router/ modem, you may have to reset it. But you need to pay attention to the fact that all the settings and changes you were applying will be lost.
When you reset the router, all the settings will be back to the default settings. Therefore, if there are settings you wish to keep, make a note of them in order to modify them once you are done resetting your router before you reset it.
How to Return the Router Modem to the Factory settings or the Default settings
How to Reset the Router ( Modem ) ?
To reset the modem, there is a reset button or hole on the back of your router. You only need to press and hold this button or hole with a pin or a paperclip. Keep holding the button inside by pushing it with the pin until the modem lights turn off and then are on again. After that, release the button. The average time of this process will be 10 – 30 seconds depending on the router type.
You may check the below two images for further explanation:
After You Reset the Modem, You Can Go Here to Learn the Default Modem Username Passwords.