Why can’t my friend access message+?

She’s able to receive a single message and open it from her notification and see the whole conversation with that person, but is not able to access her message+ Just by clicking on the app from her main screen. She has reset the phone multiple times and also deleted and reinstalled the app. Each times she tries to access it a screen pops up that says, “message+ keeps stopping.” She sent for feedback but nothing has changed. Her phone is only a year old and doesn’t have any damage.