The rotating blue light is “seed” mode where the blink tries to download the new program to any neighbors. This is a brand new pre-release feature that is not yet part of the main line that is meant to make it faster to download and test new code on a group of blinks. This mode should automatically terminate after a few spins if no other blinks are around, or you can press the button to manually cancel it.
If you are just getting started you might want to switch to the production version since it is better tested and matches the documentation.
If you are still only seeing a dark blink after the blue spin is over then something is wrong. Can you post the code that you are uploading?