making o365 login my windows login

hi all, 

im helping a friend to make one of his employees o365 login his windows login on an existing laptop and its not working. 

he's started his own company, and this is the first time he's trying this and he's got 2-3 employees he's trying to set this up for. 

he has o365 business premium 

i was able to connect his account to his domain's AD in windows accounts setttings and so he can access sharepoint, onedrive, emails etc. 

but when he switches user to try and login to windows with the o365 account it doesn't work. he gets invalid username or password screen

also in the accounts settings, i noticed its mising the info button only has "disconnect"

i was following this guide:

https://docs.microsoft.com/en-us/microsoft-365/business/set-up-windows-devices?view=o365-worldwide

is it something to do with azure? should i reload a fresh install of windows on his employees laptop and do it as a FRX?

any help would be appreciated 

thanks.