Eventbrite’s handling of payments for events has changed significantly with the release of its V3 API.
The biggest difference is that the API no longer allows you to specify which payment processor you want to use for any given event. By default, all events where tickets are sold will use Eventbrite Payment Processing.
With that in mind, you can switch to the PayPal Payment Processing method on a per-event basis. But that will have to be done on Eventbrite.com, not from your WordPress site.
Add your PayPal Email here, then scroll to the bottom of the page. You should then be able to “Save” the event without issue and make it Live on Eventbrite, which will allow the tickets to be sold from your WordPress site as well!