QNAP NAS Remote Access Test
Find whether the problem is local service access, the public TCP path, upstream NAT or simply a relay/overlay path that should not expose a port.
QNAP NAS remote access diagnosis
Choose whether you use myQNAPcloud, a VPN/overlay, DDNS/reverse proxy or direct port forwarding before running a public probe.
The public IP shown here is detected from this browser request. External probes are restricted to that same public IP.
myQNAPcloud Link does not need the same test as a public reverse proxy
QNAP documents myQNAPcloud Link as a managed remote-access option that can work without changing router settings. If that is your path, an open public port is not the success criterion.
When the TCP probe is useful
Use it when you intentionally publish a service through a manual forward, DDNS endpoint or QTS reverse proxy. Test the external TCP port clients connect to; the probe cannot verify QNAP account access or application authentication.
When it is not reachable
First confirm the NAS service works on the LAN. Then compare the router WAN IPv4 with the public IPv4 using the CGNAT Test or Double NAT Test before repeatedly editing the same forwarding rule.
Official references: QNAP remote-access documentation and QTS reverse-proxy documentation.