For those who have been frustrated because they have not been able to attach their Swan/Dolphin reservation to MDE, do not give up.
Disney IT has been working on trying to get the issue resolved for some upcoming stays. It appeared that most were resolved and attached to MDE. However, there was still one Swan reservation (SPG conf #) that My Disney Experience brought up in the system, but would not attach to MDE. The Marriott confirmation was not recognized at all. Yesterday, I called Swan/Dolphin in-house reservations and asked that they resend the info to Disney. This morning, after trying to again attach the SPG confirmation and having the same issue, as before, I tried the Marriott number, which was never recognized by Disney; MDE not only brought up the reservation, but attached it, without any issues.