Checking if your node is connected and accessible on the network

Head over to the Check Node section at this link where it says Join the Network. Input your TOR IP address in the box, but skip putting https:// at the start. If you’re using Start9 with Knots, you can find your TOR address in the Interfaces part of the Knots menu. Keep the port setting at 8333 unless you’ve changed it to something different. If your node just got reset or was disconnected, you might have to wait for at least an hour before it connects again. Click on the result to check the status.

You don't need to use a website to check if you are connected and reachable as part of the P2P network. You could just use one of the bitcoin core commands like getnetworkinfo and getconnectioncount to check that.

Based from my experience, that website sometimes can't find my node, sometimes it does. (with its onion address) While checking the "Peers" tab of the GUI usually show an inbound peer a few seconds after launcing the node (considering it's not IBD) Or use the command suggested above: getnetworkinfo to check if your preferred network is "reachable: true".