This must be some USB problem but when I connect the drone to my Win10 computer the computer makes the usual usb connect sound but the drone does not show in Explorer so I cannot download the photos so I have to remove the SD card and plug that into the computer.
Now here is the weird thing, although the drone does not show up, DJI Assistant happily connects to it !
Any suggestions?

You may check in your device manager in Windows. If you find any more COM ports listed than COM1, uninstall the additional ones completely. It is also worth trying another USB port on your PC.

Thanks, I only have Com1 showing in Device Manager and the other USB port gives the same result. Its strange that Assistant connects to the drone OK. I think its some sort of driver issue.

Hmm, discovered another usb connection on the back of the computer so I tried plugging the drone into that one. Now, in device manager, as well as COM1 I see DJI USB Virtual Com (Com4) and DJI USB Virtual Com (Com7)
Are you saying I should delete the Com4 and Com7 ?

Why not eject the SD card from the done and plug it to your PC?

PatrickW Posted at 2018-9-29 11:08
Hmm, discovered another usb connection on the back of the computer so I tried plugging the drone into that one. Now, in device manager, as well as COM1 I see DJI USB Virtual Com (Com4) and DJI USB Virtual Com (Com7)
Are you saying I should delete the Com4 and Com7 ?

Yes, but not only delete, right click on them and choose uninstall, chances are high that it will work thereafter on that rear USB port. I have had the same problem on my PC and bought a USB cable extension to make the solution comfortable.

Eagle_Eye Posted at 2018-9-29 11:43
Why not eject the SD card from the done and plug it to your PC?

Thats what I have to do at the moment. Opening that little hatch then trying to extract the SD card is not easy

Wachtberger Posted at 2018-9-29 11:49
Yes, but not only delete, right click on them and choose uninstall, chances are high that it will work thereafter on that rear USB port. I have had the same problem on my PC and bought a USB cable extension to make the solution comfortable.

OK, I uninstalled them but still cant see the sd card. When I unplugged the drone and plugged it back in, the extra com ports showed up again.

PatrickW Posted at 2018-9-29 12:05
OK, I uninstalled them but still cant see the sd card. When I unplugged the drone and plugged it back in, the extra com ports showed up again.

I have sent you a PM with an alternative approach. Hopefully it will work then, kindly let me know.

I am glad to learn from your PM response that all is working well now :-)