The flashing green part means that it's trying to connect to something, so you should be able to add it now.
If that doesn't work, do you have anything USB 3.0 plugged in? As some USB 3.0 cables can cause interference with the 2.4GHz band.
We've done our best to try to limit the interference, but we found that certain cables still causes problems.
That said, considering the other sensors worked fine, there might be something wrong, just want to double check everything before we'd arrange for a replacement.