If you have participated in Zoom sessions before with your device, check to see your app is up to date.
Possibly, go to  http://zoom.us/test to check your settings.  Then go to #2.

1. Set up your device for Zoom

• Download and install a Zoom app for your device
• After installing, visit http://zoom.us/test to join a test meeting. Here you can familiarize yourself with Zoom, in addition to testing your microphone/speakers before joining a Zoom meeting.

2. Setting up your Zoom environment

• Lighting should come from in front of you or from the side, in order to best light your face. Eliminate any direct backlighting (like a window behind you).  Get plenty of light overall — be aware of glare on any eyeglasses.
• Keep your background clear of distractions
• Have the camera of your device/laptop at eye level.  Put the device/laptop on a box or some other sturdy support such as stack of large books to adjust the camera to eye level
• Smartphones or pads with cameras can be used but must be used in a horizontal or landscape position ^▄ not portrait  ▌and should be used with a stand or not hand held.
• Avoid noise and other sounds at your space.
• Choose solid-colored clothing rather than clothing with tight patterns or logos.