I tried to access the Gateway, but it is not working, and I don't know why. I have several gateways, and the other one (on the browser tab next to it) is working normally.
That "Not secure" in the browser could mean you are trying to access the gateway with https:// in the URL but at the non-secured http (8088) port.
I have actually had this issue a lot, I have never found a reason for it but occasionally a gateway will just serve a blank page and continue to do so for every previously working client until you reboot it.
It has happened on multiple versions of Ignition, but mainly when I am on the initial stages of a rollout of a gateway. I don't seem to remember an established gateway in production having this issue.
That's true, I have several gateways that have been operating for over 3 years. Meanwhile, the gateway experiencing the blank page issue is a new gateway, less than a month old. I don't understand what causes this.