Q: photo stream download problem

My daughter is e-mailing me inviting me to join her photo stream, but her e-mail isn't coming to my phone (all my other e-mails are), it is just coming to my computer, then when I forward it to myself, it comes to my phone and try to join, it says this photo stream is no longer shared.  What is wrong?  My other daughter invited me to join hers, and it went smoothly.