There are several limitations for Webex Scheduler for Outlook for non O365 and non hybrid calendar deployments (Exchange onPrem without hybrid calendar), f.e.:

• Meetings in a series only show up as a single meeting in the Webex calendar.

As you can see in article https://help.webex.com/en-us/article/n194fs/Known-issues-and-limitations-for-the-Webex-Scheduler-for-Microsoft-Outlook

This is a feature request to add functionality, that Webex Scheduler for Outlook does create repeating Webex Meeting according to the recurring Outlook Meeting for such deployments.