First get an access code from your TTN profile by going to
https://account.thethingsnetwork.org and clicking "ttnctl access code".
.\ttnctl-windows-amd64.exe user login [paste the access code you requested above]
INFO Successfully logged in as yourname (your@email.org)
Now you can query the gateway status:
.\ttnctl-windows-amd64.exe gateways status <your_gateway_EUI>
INFO Discovering Router...
INFO Connecting with Router...
INFO Connected to Router
INFO Received status GatewayID=<your_gateway_EUI>
Last seen: 2020-06-24 11:28:32.866382977 +0200 CEST
Timestamp: 0
Reported time: 2020-06-24 11:28:21 +0200 CEST
Platform: The Things Gateway v1 - BL r2-c463e87e (2018-02-23T14:42:40Z) - Firmware v1.0.7-e9d35a30 (2019-06-19T11:00:19Z)
Frequency Plan: EU_863_870
Bridge: gs.v3.
Location: not available
Rtt: not available
Rx: (in: 13891; ok: 13891)
Tx: (in: 70; ok: 70)