As of 31 May, version 5 of the Zoom client is required to participate in a Zoom meeting.
You can see which version you have by clicking on the circle in the upper right corner and then follow:
–> Help –> About Zoom
If you do not have an updated version, you will be required to update before connecting to, or starting, a Zoom meeting.
You can read more about the update here
Content checked / updated 2020-06-04