I'd start with turning the router off and on again. That sometimes helps to reset it.
Then I'd go into the router management page via a wired connection check all settings (including encryption, protection, mac filtering, passwords) and maybe temporarily set them to default.
Then I would find a wireless device to connect that gives clear error messages. I've solved a connection problem between my sons Wii and our router by checking the error number the Wii displayed on google and doing what everybody with that error number did.

Of course, there's a chance your router has become defective. Then you would have to buy another one. There are no clues at all in your post to tell.