I'm experiencing the same thing. I'm one member of my sister's Office 365 family subscription and yesterday I got the "cancelled" message on all products. Problem is, while trying to resolve it, my sister removed me from her members list and re-added me. I received an invite but was unable to join because I got a message I was already a member of another family group (which is true since I'm in a family group with my own kids).
So did I botch up my chance it will resolve itself? Is there anything special I need to do to get this fixed? Or will it automatically resolve itself since I'm on my sister's members list?
Thanks in advance.