Wireless Bluetooth keyboard won’t turn on.

Thank you. The last section of this Apple article says of the A1314:

Set up your Magic Keyboard, Magic Mouse, or Magic Trackpad with your Mac - Apple Support

says:

* If the LED turns on briefly but doesn't blink, the device might be connected to another Mac that is nearby. On that Mac, choose Apple menu  > System Settings (or System Preferences), then click Bluetooth. Click the Show Detail button , then click Forget This Device. Or move your pointer over the device's name, then click the remove button . After removing the device, turn it off and back on.

Long shot: Some older Apple wireless boards used three batteries instead of two. The third battery sometimes became stuck, and could look like the bottom of the battery cavity. It would not get changed because users thought the board needed but two.

You can quickly see whether you have a two-or three-battery variant by flipping the keyboard and looking for the tiny icons on the battery "tube" at the battery cover end. This board is a two-battery variant.

Otherwise please find the model of the board on its back— should be A000 format—and post that. That might stir up more clues.

I have the same issue: the keyboard is not connected to any other devices, it just won't stay powered on. The green light appears for a few seconds when I hit the power button (solid, not flashing), then disappears. A few times the keyboard appeared in the Bluetooth devices list but no longer. Batteries are brand new.