Do you mean that you already have a Windows boot camp installation on your Mac?
And, you don't need to boot to Windows on that external hard drive?
In that case, boot to your boot camp Windows partition, then try to access the external hard drive then.
You can see your boot camp partition (or not!) when you restart while holding the Option key.
I suspect that the hard drive is no good, but you should certainly try to access the hard drive from Windows.
I also think that your external enclosure is bad, too, but trying it while booted to Windows may help - or it may simply also not work at all from Windows.
And, you don't need to boot to Windows on that external hard drive?
In that case, boot to your boot camp Windows partition, then try to access the external hard drive then.
You can see your boot camp partition (or not!) when you restart while holding the Option key.
I suspect that the hard drive is no good, but you should certainly try to access the hard drive from Windows.
I also think that your external enclosure is bad, too, but trying it while booted to Windows may help - or it may simply also not work at all from Windows.