If you have installed UC for your AudioBox, but your AudioBox will not show as a connected device within your software or any software, then you may have a bad connection or a faulty AudioBox. Contact PreSonus Support for assistance.
However, you do mention that you are able to get at least the left side thru your software. This may be because most streaming software, even Skype for example, can only use WDM audio drivers. WDM audio drivers are mostly used in pairs. Channel 1 and 2 or a Left and and Right signal. It is up to the software you use to use only a single input at a time. Some streaming software do not let you choose only a single input channel. Thus if you are using a single input channel, you will only hear it on one side.
There isn't much you can do about this.
However, you might consider a Studio 2|6 over the AudioBox. The Studio 2|6 has a virtual loop back feature. This allows you to virtually route the main out audio back to a stereo input for streaming software.