Came across this a few years ago when I tried NextPVR, and got it working, but now I'm stuck again.....
Fresh install of NextPVR on Windows 10, go to localhost:8899 and get the login page, but it does not accept the default password (admin/password).
Deleted config.xml, tried again but no change.
What have I missed..... I cannot for the life of me remember how I got round it last time.
Tried Firefox and Chrome, no plugins etc.