Is is possible to disable a participant's virtual background?

Thank you for reading this.

A friend of mine encountered this problem a few days ago in a Zoom online event. The problem was that her virtual background was automatically turned off once joining that meeting and she could not enable it. She had never seen such situation before and her computer worked perfectly fine with virtual background(still perfectly fine now). She also told me that during the meeting it was just her having the problem coz others were all doing well with their virtual background.

I've tried to simulate the case with my friends but we ended up nothing. so I wonder how this happened:

1)Is it possible for a host to do so? Or

2)is it possible to do so with the meeting setting functions? 

Otherwise,  I think it was likely due to an unknown bug on her computer.