Invited Collaborator cannot view folder

I have invited a person to collaborate with a folder several times and she cannot access the folder. It's not in her list and when she uses the link in the invitation emails, she gets a message, "Oops! We can't seem to find the page you're looking for." I have removed and re-invited and I've tried sharing an individual file in the folder and she cannot any of these items. When I look at the collaborator's list, she is listed there, but her little name dot is gray, while all the others are blue or purple.