I have set up two origin IP.
Origin IP 1 192.168.0.1
Origin IP 2 192.168.0.2
Our sites are using Windows IIS.
I have set application host config on both two servers.
When I turned on the load balancing and stop the 1st origin IP, domain abc . com did not failover to the second Origin IP but it returns error 1016.
Assuming those are the actual IP addresses, none of the records (nor the load balancer) can be as those are private IP addresses and Cloudflare can not proxy that traffic (nor can it do health checks to know if an origin is up or not).
Without knowing the actual IP, I would recommend opening a support ticket (support (at) Cloudflare (dot) com) where they can look at the actual values used to perhaps provide some information.