I think you are best off asking My Heritage . . .
Dennis is right.
However, do you know the FS PIDs for those spouses that are being rejected? FS has provided the ability to have same gender couple relationships and along with that, the ability to swap their positions in their tree. But regular couple relationships can get "glitched" in FS where the man and woman are reversed. My Heritage probably can't handle that unusual arrangement.
These positions can be swapped back if you know the PIDs of the spouses involved