There's no IPNs at all within CBSubs > Notifications. Did you not configure Webhooks within your Stripe account? There's only PDTs there. You need webhooks for recurring payments otherwise Stripe won't notify CBSubs that a subscription was renewed. Edit your Stripe payment gateway and review the configuration under "Stripe Webhook Credentials" carefully. Note you only need to have Stripe send the webhooks listed in the Stripe gateway configuration and it's not recommended to send all webhooks.

If webhooks are configured they may not be reaching your site. To verify this login to your Stripe account then under Developers > Webhooks > YOUR_WEBHOOK check the webhook log. We respond to all webhooks with a message to confirm CBSubs received it so it should have a response body of some kind (e.g. "webhook skipped: already processing (idempotency)", "webhook process: success", etc..). These should have a response code of 200.

1. Just so I better understand.  The webhook function is what syncs the user data on the site to Stripe.

It's strictly to allow Stripe to let CBSubs know state changes of user subscriptions and payment status. So for example when a subscription renews it will tell CBSubs that it renewed. If a payment is pending then it will tell CBSubs when the payment is successful. It's important, but for single payments 99% of the time you'll be fine and don't need webhooks, but it's still a good idea to configure them.

2. I should only select the events noted in my backend (shown below) rather than "all events".  Is that correct?   Along those lines, I only see "customer.subscription.deleted" - should this cover me for when memberships renew by recurring payment or do I need to look at other events?

Yes, you only need to select the notifications listed in CBSubs Stripe. It won't do any harm to CBSubs if you select all events as we just ignore the ones we don't process, but Stripe would be unnecessarily communicating with your site by doing that.

3. Once the webhook is set up properly, will it find the 3 users that were not synced to Stripe or do I still need to manually activate them this year, but come next year it should sync up again?

If those 3 users are already broken you need to fix their subscriptions as instructed earlier and then yes renewals should work fine.

As for webhook version yes you can use the latest version. We have versioned API AND versioned Webhook support so we're backwards/forwards compatible. A LOT of work has gone into making Stripe our most robust gateway to date.