Can't connect a new controller the power button keeps flashing on and off slowly

Have you tried a full power cycle/shut down of the console yet?

When this happens with my controllers, I try that first. If that doesn't work, I connect the controller with a console. Typically the full power cycle clears up the issue.

The controller cannot pair with any computer, in fact it is not even visible on any computer. As I said, the Xbox button on the controller flashes slowly when I press and hold the button but as soon as I let go it switches off entirely. Pressing and holding
the Xbox button for a slow flash and then simultaneously pressing the sync button, which would usually result in a fast flash, does not result in a fast flash, it just keeps flashing slowly. When I plug the device into an external power source, the Xbox button
slashes slowly but the sync button still does not cause it to flash more quickly and it is not visible to any device. Thus I am quite sure that it is not a problem with the computer but with the controller.

Restart the console Connect the controller again using the console and the connection button on the controller then it should work.

I already tried the sync button on the remote but nothing( it only keeps on flashing,slowly)

I will try it again

Yes, I'm trying to connect my controller via Bluetooth on my Windows 10 PC (It worked before yesterday). When I connect my controller via USB Cable it works fine.

The XBox Button flashing slowly when it's turn on. When I press the sync button to connect via Bluetooth, the XBox Button flashes for 1 second and the controller turn off.

i have tried disconnecting it and then reconnecting it and now the controller doesnt work on the laptop at all, it keeps going from connected to paired then back to connected and the xbox logo on the controller is flashing slowly.