Medicare is saying there is a conflict of interest with my doctors. What does this mean?

While I am being treated for cancer away from home, my husband and I are living in a assistant living facility. Because I don't have a primary care physician here I am using one of the doctors that the facility uses. I've been told by my oncologist's office that they are not receiving payment for my office visits, that Medicare says there is a conflict of interest which I don't understand. This has not happened to me in the past. Does anyone know why this is so?