Zoom - Virtual Backgrounds
Difficulties using Virtual Backgrounds
Zoom Virtual Backgrounds can be enabled or disabled on individual user accounts, AND on individual meetings.
The creator/scheduler of a meeting can disable virtual backgrounds for a specific meeting. This is also a setting that can be default for an account, so people may disable virtual backgrounds for others in their meetings without realizing it.
If the meeting has virtual backgrounds allowed yet they still are not working for your account, here are some troubleshooting documents from Zoom.