Here we are
Currently there are two methods working (on mine scooter at least) :
THE FIRST WAY
via chinese app, apparently the same one as founded in the web (which doesn't work) last weeks but, with some slightly graphics differences and overall, different codes. With this app you can unlock the full speed: after inserted the code, the scooter confirm with two beep and after restarting the word "sport" into the display became red and you can reach 40kmh.
Options available in the segway app remaining the same.
THE SECOND WAY
change the serial number, via downG app, you need to create a new segway account (you can just log out by the older) and register your device with the new modified serial (find vehicle will recognize your device as a new one) you will get an original US device with all option enabled, cruise control, park mode, all settings for speed enabled. The maximum speed available will be 32kmh, the option "boost speed" remain unavailable.
I'm still in testing mode but I'm pretty sure that if you apply the first way and then the second, you will get ALL OPTIONS WITH FULL SPEED
The only doubt, repeating, is the version of my scooter "E" by yours "D" but as my results it shouldn't make any differences and it's worth to make a try.
That is what I've done.
Hope I had been pretty clear, it's hard to explain with the right words but it's very simply and safe to apply. For any questions I'm still here.
if you are interested I can find a way to upload application and codes. Greets
Here are an attachment with the final results (wheels lifted up obviously

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Anhang anzeigen 44420