Why is Netflix blocking a /64 of our /36 IPv6 BGP network?

Netflix may be blocking your /64 due to abuse or suspicious activity originating from that specific subnet. Since you have a large /36 network, it's possible that one of the /64 subnets has been used for malicious activities, leading Netflix to block it. To resolve this, you should investigate the traffic originating from the blocked /64 and ensure it's not being used for any abusive purposes. You may also need to contact Netflix to report the issue and provide evidence of legitimate usage.