i have a problem setting any images as background during a meeting. The image that you can see is a mix between the backgroung and the real image from webcam. All colour are mixed and my background remain visible and coloured.
Having a busy background like a bookshelf, a wall with lots of photos, or a window will make it harder for Zoom to differentiate between you and your background when trying to use a virtual background. Try having an empty wall behind you, if you don't have an empty wall you can try hanging a white sheet behind you and see if that helps.