I have a similar situation..
Was able to login using trueNAS on my local network for a while. I tried rebooting and the TrueNAS access also ceased. My local network shows the server is not connected to the router from this point on, no matter how many reboots I did!
I was able to boot using older version but all my apps and storage folders are missing. At least it is discoverable after this.. Applied update again and that seems to have fixed it. All the apps and shared folders are functional.