Switching Child to Another Family Sharing Account

My daughter's child account is listed under her Mother's family sharing account. I sent an invitation to have the child account transferred to my family sharing account (father). My daughter received the invitation as a text message on her iPad. However, the organizer (Mother) did not receive any notification. Clicking on the invitation on my daughter's iPad does nothing but explain the child can't accept the invitation and the organizer would receive notification of the invite. (This is completely not true.) Another post in Apple Support stated to try looking in the organizer's account under iCloud: view and change family sharing settings, but there was nothing there. Her Mother's account is the only family sharing account she has been associated with.

Does anyone know why the organizer is NOT receiving any notification of the invitation, and know what we can do to make the switch?