Hi Edward,
Do statuses you mentioned(Invited, Registered...)also exist in WebEx?
Or are they just your custom optionset to track contact status?
As per my understanding towards your description, you could take process below as reference, it only requires low code to complete integration.
1. Create an optionset field with statuses you mentioned for Contact entity.
2. Create a flow in Power Automate, it contains 5 actions:
Act1: A HTTP Request Trigger, it will give us an automatically generated endpoint URL to process custom request.
The last answer of mine in thread below introduced how to use the trigger and how to deploy it to marketing page.
https://community.dynamics.com/365/marketing/f/dynamics-365-for-marketing-forum/385271/thank-you-email-after-every-form-submitted
Act2: List records(Common Data Service), it is used to validate whether submitted data could match to existing contact record to prevent malicious registration.
Act3: Condition checker, if result count from step 2 is larger than 0(If existing contact is found), then goes to Yes branch.
Following tutorial is about how to get record count from "List records" action.
https://powerusers.microsoft.com/t5/General-Power-Automate/Get-record-count-of-Dynamics-quot-List-Records-quot/td-p/306269
Act4(In Yes branch): Add "Cisco Webex Meetings" connector to push submitted data to WebEx.
Here is article from Cisco documentation about how to use the connector in Power Automate.
https://help.webex.com/en-us/nv1s5rm/Cisco-Webex-Meetings-for-Microsoft-Power-Automate
Act5(Still in the branch): Set the matching contact status field to "Registered" with "Update record(CDS)" action.
3. Create a landing page, add marketing form to the page, send a XHR with submitted data to the endpoint(from Act1) at formSubmit event.
4. Attach the page link in marketing email to send to your contacts, they will complete registration by submitting form with their data.
5. Create a customer journey to deliver marketing email to contacts, trigger a workflow when email is opened, it will set recipient status field to "Invited".
For other statuses: Attended, No-show and On-demand, I'm not sure how do you manage them, so I assume you could manage them manually.
If there are contacts whose status equals to "No-show" or "Attended", then run another customer journey to send out follow-up emails.
(Currently WebEX connector in Power Automate can only add people to a meeting, I don't know whether WebEx also saves attendee as records, likes we save a contact as record in Dynamics Marketing.
If the functionality exists in WebEx, you could request WebEx API manually with HTTP request action for retrieving attendees.
https://d365demystified.com/2020/04/07/make-http-request-from-flow-in-power-automate/)
Regards,
Clofly