I got my red bear duo from the recent mass drop. Initially I was able to get the duo connected to particle build, but after trying to install an example application it stopped working. After a ton of random flashing I have things working again. Two pages helped get things going again.
The first link has information about flashing to the duo, and the second was used when the firmware was updated, but the device still wasn't connecting to particle build.
Hope this helps others.