Since noone responded and i really need the webhooks integration, I decided to get a RapidSSL certificate instead of a Let’s encrypt one, however the test platform still gives me certificate invalid errors.
Dear patreon server admins:
Please add Let’s encrypt and DigiCerts Root CA’s to your trusted list (or allow unsecure requests)
Are you sure that the problem isn’t to do with your server configuration? I’m using a Let’s Encrypt certificate for my webhooks and I have no problems.
Actually, I found your domain in your screenshot and looked at the SSL Labs test for your domain and it’s showing that your SSL configuration is incomplete. You need to resolve that issue: this problem isn’t specific to Patreon, there’ll be other clients having issues accessing your site over HTTPS.