My router supports up to four different virtual access points for WiFi on a single router / unit. Some of the Virtual Access Points have Key Regeneration turned off, and the other Virtual Access Points have it turned on. This allows me to work with the capabilities of each device. Some devices are connected to one Virtual Access Point with Key Regeneration disabled, and the other devices that work better with Key Regeneration are connected to the Virtual Access Point with Key Regeneration enabled. This setup has solved my iphone / ipad issues, and still allows my other devices to operate with regular Key Regeneration timing that changes the encryption keys every hour as defaulted or expected on most routers.

I have seen videos where if the wifi chip is bad or the connection for the wifi chip is bad, loose solder joints under chip, it causes the wifi chip to be unavailable or undetected. If your WiFi is grayed out, and there is no option to enable / disable, I would take the device in for warranty exchange or repair.

What brand model Wifi Router or what brand model Access Point?