Password help

I can login to my router at routerlogin.net.  I can not log in to the Nighthawk app.  I have tried every password I can think I might have used.  In the website there is the optionto change a password but it asks fo rthe old password & no matter what I put in it says that it is incorrect.  Before this happened I had reset the router because I could not log in on my computer.  Any suggestions would be appreciated.