ANSWER:

If there is a coating or a layer above the nail preventing water from reaching it, such wudhu is invalid and al prayers prayed are also invalid.

You must remove this layer. If it is not possible to remove it, you must perform wudhu and also tayammum for skipping washing the nails every time you want to perform wudhu.

A few weeks ago I used nail buffers(both sides) my nails are not shiny anymore, but are still smooth (indicating the effects of it still hasn’t worn off). My question is: do nail buffers prevent water from reaching the nails? If so, will prayers not be accepted? What should I do now since there is no way to reverse it? (nail buffers work by chemical reactions) thank you for your time.