Hi,
in order for us to help, you will have to give way more information. Is the service you are trying to connect to hosted inside a VM or on a different host? Are your VMs in the same subnet as the service you are trying to reach? Is the firewall enabled on datacenter/host/VM level?
Please share your Proxmox VE's current network configuration /etc/network/interfaces
and the configuration of the VM you try to connect from qm config <VMID> --current
as well as the config for the VM the service is located on (I assume it is a VM, share the network config for the host otherwise).