Thanks for reaching out!
The power supplies you used should work with the mini breakout board, and as you mentioned, in J21, the ground is closer to the edge as can be appreciated on Figure 2 of the Hardware Guide (http://www.intel.com/content/www/us/en/support/boards-and-kits/000005574.html). So, the steps you have taken sound fine. I would like to see how you are connecting the board to the power supply, could you please send us a picture of this?
Also, if you have access to an Arduino expansion board or a different mini breakout board, could you please test powering the board on a different expansion board? If so, let us know how it goes.
sorry for late answer, I haven't worked on this project last two weeks due to my work and I kind of forget about my question here.
In the end, it was combination of bad luck and my mistakes - the first adapter I tried was not working properly and didn't provide enough current. The second was OK, but I forgot to check polarity on the second one (I checked it only with the first one, the second had the same colors of wires as the first one but polarity was actually reversed). Once I switched polarity and used second, properly working 9V adapter, everything was working OK.
That is great news, I'm glad to hear that you are now able to use your board normally.
If you ever have any other doubt or question, please don't hesitate to come back to the community. We'll try to help you in any way we can.