Black screen

I am getting a black screen when I use my iPads to open a video using QR code reader.  These QR codes  have worked for me all year but I'm not sure why they are not now.  It appears as if the safeshare site is opening but the video box is just black.  Please advise, I am a teacher and use the QR codes to share videos and other information with my students because of how safe and independent it is.