For those who are getting an error activating this builds no matter what you do, You can do this steps!
1- Go to Settings > Update & Security > Activation
2- Go to "Change activation key"
At this point doesn't matter if you already tried to changue it for this keys. Do this step to go to next step!
For Windows 10 Insider Preview Home Editions: KTNPV-KTRK4-3RRR8-39X6W-W44T3
For Windows 10 Insider Preview Pro Editions: 8N67H-M3CY9-QT7C4-2TR7M-TXYCV
For Windows 10 Insider Preview Enterprise Editions: CKFK9-QNGF2-D34FM-99QX2-8XC4K
Click NEXT, And It will say "WINDOWS COULDN'T ACTIVATE WINDOWS WITH THIS KEY"
AT THIS POINT THAT DOESN'T MATTER! DO NEXT STEP!
3-Right Click at start button, and select Command Prompt (Admin)
4-In CMD, Type slui.exe 4
YES THE 4 IS NECESSARY. INCLUDE IT.
5-In the windows there is a phone number. Go to your home phone or smartphone and call it. IS FREE AND IT IS AN AUTOMATED VOICE.
6-While you are calling press NEXT. You will now see a very large number in groups, this is what you will use in the automated call.
6-Follow the instructions to get to activation of windows, office and other products in automated call (In some point it just says press one to office activation) If is in a loop press 2.
7-Listen the instruccions, you will be need to enter pressing the numbers on your phone the large code in groups while the voice is telling you each group.
9-After you finish it will say click NEXT and you will need to enter a code. It will tell you the code. Then Click NEXT and that's it.
10-Windows will be now activated. just click exit!