Sign in with a local account instead - password issue

You first need to use your Microsoft password to access or authorize the change to local account- then you make a new password, and secret on the form ...  it can be the same as your online password if you like - but it can be a totally different password too.

I am using my Microsoft password, but it doesn't work when it enter it, after i've pressed the "settings/sign in with a local account instead" link.

The password works when I press the "manage my microsoft account" link above, on the same page in the settings.

I'm thinking it's a bug?

Can someone from windows support team tell me if this is a bug?

The correct Microsoft password doesn't work, with the link "sign in with a local account instead"!

I'm an extremely proficient computer user and have been failing, for 3 days now, to get the family protection working in windows 10.  

I designed and built an android app in less time!

do i have to:

a) Delete all but one user account, and start again (instructions please - i cannot remove an old linked microsoft child account even though i've deleted the account online it remains on my machine!!!!)

b) reinstall windows 7?

c) move to linux?

COME ON MICROSOFT - SORT THIS OUT!!!