Uploaded images are seen as grey shapes by my team

Hi everyone.
I’m a teacher, and I teach my students on Miro. I normally uploud pictures, screenshots and the like, and my students see them. But today my student siad he saw just grey shapes instead of my pictures. So they’re uploaded, I can see them, but not my students. It/s the first time my student hasn’t seen pictures on Miro. I’m in Russia, he’s in another country, which is probably the cause of the problem. Or no?