I installed Proxmox using the 8.4 ISO on my Dell PowerEdge R420 server, but I'm unable to ping my gateway. I need help with the network configuration and look forward to your response. Thank you. when i ping gateway the output is no host unreachable
You have enp8s0f0 as bridge-port for vmbr0, which shows NO-CARRIER (= no cable inserted / cable broken usually).
enp8s0f1 seems to have a cable connected though, so easiest would be probably to just plug the cable into the other port and then reboot.