What about the voltage to the strip? Also, what exactly on the Arduino is that power supply plugged into?
@marmil I have found that you cannot bypass a pixel and connect to the next one unless you cut the strip. The previous pixel’s Dout eats your signal (well, at least it did on the strip I tested).
@DEX_20 you can buy this to verify your neopixel strip: https://www.amazon.com/gp/product/B01LZ3VUQI but odds are that there is something wrong with it.
You may even have received a strip that does only white (yes, they do exist).
@Andrew_Tuline the voltage when strip is conected is 4,8V i have all grounds together.
@DEX_20 basically don’t expect that the strip you have, actually works. You do get what you pay for on aliexpress :-/ (not saying that I have nothing from there, but I don’t have a high expectation that everything will work)
@Marc_MERLIN i know, but normaly all thing i order work fine.
@DEX_20 true for me too, so this order may have reset your odds to baseline 
(but more seriously, you should see some of the “worst of” crap I’ve gotten from china, including a GPS chip where I received just the PCB and the GPS was not even soldered onto it)