I just checked and found both of your grandmothers. Their IDs are Shelton-562 and Stone-1996. Those links will take you to their pages.
I think I see your problem now. They both have a profile manager named Curtis Shields so you need to contact him and ask to be added to the trusted list for them. Then you will be able to connect them as mothers of your parents. You might want to also ask to be added to the trusted list of other family members, if it turns out that he is also profile manager of them.
To contact him, you can send him a private messge - if you click on the link to his page that I put above, you will see a place on the right side where you can click to send him a private message.
WELCOME TO WIKITREE!!!