At this moment I got www.example.com attached to a load balancer. These load balancer is attached to server1.example.com and server2.example.com. I am using SSL Full (strict) with Cloudflare origin certificates. Everything is okay.
But when I acces server1/server2.example.com I got a security message because the Cloudflare origin certificate is self-signed. I understand that.
Today I bought a server1.example.com Sectigo certificate and installed it instead of the Cloudflare origin certificate. Now I can access server1.example.com over HTTPS without any problems or security warnings.
But the problem now is it is not working anymore in my load balancer. I got understanding message mailed because of an failure:
Tue, 11 Jun 2019 10:09:34 UTC | DOWN | Origin example1 from Pool example1 | TLS untrusted certificate error
Why is it untrusted? Google Chrome is trusting it, why the load balancer / Cloudflare not? Is it only possible to make use of it with origin certificates? Why not with a regular signed certificate?