Update templateVM through vpn-proxy

This suggests you haven’t enabled the proxy in the vpn qube - the service
is tinyproxy
Depending on how you set up the proxy, it’s also possible that your
firewall configuration on the vpn-proxy is blocking traffic to/from
tinyproxy.
Try enabling the service with qvm-service and see if that works - if
not, you’ll need to provide more information.