Cannot upload sketch to a genuine Leonardo

Can someone help me get a Leonardo connected to my laptop via USB.
The board hasn’t been used for a few years.
It worked like clockwork with an ancient dell running Xp. The original laptop has been reloaded since last used with the board so I can’t just plug it in and check it out.
I’m trying to get the board communicating on a Win10 laptop using the current software version.
When I connect the board, the board pwr led is on, the yellow L LED glows, I get the USB “bing bong’ , and in the device manager under ports I see “Arduino Leonardo boot loader” and COM6 allocated. A few seconds the L led goes off , I get the “bong bing”. And the device disappears from the com port config.
Windows sets the board to COM6, in the software there is a choice of COM3 and COM6, I set it to COM6.
I compile the demo blink sketch, and when I attempt to upload get this error ….
caused by: jssc.SerialPortException: Port name - COM6; Method name - openPort(); Exception type - Port busy.
at jssc.SerialPort.openPort(
... 6 more

When the sketch starts to upload , only the board power led is active.
I’ve since installed ver 1.0.5 on the ancient laptop under Xp and get a very similar issue. Different USB cables have been used. Reading the Leonardo Getting Started Tutorial didn’t help. Plus I found a couple of posts on the forum very similar to my problem which didn’t help.
I've looked through the help in the Arduino app to no avail, and have tried the current version plus a very early one,, The pc usb port works with flash drives, I’ve tried a couple of different cables.
Hopefully the USB port on the board didn’t die whilst the board was on R&R.

Can anyone point me addition info to track down the problem, I’m pulling out hair over here.

Does anyone have suggestions on what I’m doing wrong.

If there is any wiring/circuitry/shields/modules/etc. connected to the Leonardo, try removing it and connecting just the Leonardo alone to your computer. Also take a look at both sides of the board to make sure there isn't any conductive debris that might be causing a short, plus make sure it's not sitting on anything that could cause a short.

The board has nothing connected except of course the USB cable.
Its sitting on a clean work top, defiantly no conductive debris there.
And the board has a little dust on it , doubt its conductive but I'll wash it down with a little alcohol .


When the IDE reports the memory usage, press and release the reset button on the Leonardo. That will get it in bootloader mode.

It's strange that the board goes in bootloader mode after power up. I would start by uploading innocent sketch like blink.

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