Looks like the "web" service is not starting and/or is crashing. Don't know what PVE uses for http service, Apache or something like that.he can ping and ssh into PVE, his local curl command ran from PVE shell to PVE IP hangs. I'd say the issue is in services, not in network.
As an additional test try:
curl -sk https://127.0.0.1:8006|grep title
If it works, you should see something like:
<title>pve7opt6-1 - Proxmox Virtual Environment</title>
P.S. if it still hasnt rebooted - press the power button
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