Cause: 
The issue occurs due to a certificate mismatch when converting a Webex trial subscription to a paid subscription.

Solution:

To resolve this issue:

1. Open Webex.

•  Click on your profile picture > Select Settings > Click General > Uncheck Start Webex when my computer starts.

• In the Apple menu bar, click Webex > Select Preferences > Uncheck Start Webex when my computer starts.

2. Uninstall the Webex app.
3. Restart your computer.
4. Re-install the Webex app and attempt to login.

Note: If there are other users present in the Webex space, the moderator must have all participants leave the space or remove them from the space.