Problem on connecting to a wireless router: Microsoft

The latest Microsoft operating system has restricted access to wireless router.
I am currently using the latest operating system version of Microsoft and going online has been easy for me. When I decided to activate the protection settings of my wireless router, my computer suddenly cannot hook up to the connection.
I have other several devices like portable computers, another personal computer a gaming console and android mobile phones that can easily use the internet via the wireless router but one particular computer has restricted permission even if the signal it detects is strong. Can you please explain why this happened and how can I resolve this so that I can have this computer go online again?
