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The problem may be quite simple, really. When a USB-cable-connected device gets power, charges up with that power, but is not recognized as a device by the computer, then the Data lines (2 out of the 4 lines in a USB cable) is one or both of them occluded by dirt, broken, cut/snapped, or otherwise defective.
1. take an old (but clean, and dry) toothbrush, and scrub out the USB ports (with the power Off!) and the USB plugs of your USB cable. Then try again.
This problem commonly is caused by dirt, even just a little, or sometimes a slightly loose or slightly strained cable.
Also try a different USB port on the computer, or several of them. USB ports should be all alike, but very often are not in actual fact.
And as the last thing to try, swap out the USB cable for another one. Esp. if it looks strained, was yanked on at any time, or is severely (and/or repetitively) bent at any point.