Having reviewed this I believe that your Paypal is possibly configured to point to an older version of the IPN path.
You can change this yourself within your Paypal account, the docs I can see suggest:
To configure Instant Payments Notification (IPN) for your PayPal account Click: Profile, under Selling preferences click "Instant Payment Notification ...
If you think the webhook URL is correct and the extension is still printing the error message on the status page and the same is also not getting fixed by Fix Stripe Webhook, make sure -
You have correct latest API version set for your webhook.
Only a bunch of events are enabled for triggering the webhook instead of "All Events". The events currently ...
I would follow the instructions on screen:
Log in to your Stripe account, go to the Webhooks section
Delete the existing webhook (on live and testing sides)
Come back to CiviCRM and use the "Update/Create Webhook" button