No Active Bridge is Selected

I have an OBM model built in a separate 3D file (File A). I referenced that dgn into a new dgn (File B) to create multiple drawing and sheet models. I have created mutliple 'drawing' models within File B with no problems. However, for the past few days, OBM won't let me create any more drawing or sheet models. Every time I try to create one, it says 'No Active Bridge is Selected'. I know there is something I'm probably missing between the two files, since it already let me create multiple drawing models with OBM in the same file previously. Since the OBM model is referenced, the explorer window does not show any bridge.