I had a very similar error to this. When I typed in the IP address of the admin page I received this:
[snip]
I restarted my unRaid server and this error still persisted.
Used SSL to get into the server.
ran the /etc/rc.d/rc.nginx status command, the result was:
"Nginx is running"
typed the commands:
use_ssl no
/etc/rc.d/rc.nginx restart
I was then able to get to the admin page and start the array.
hardunraidtower-diagnostics-20220414-0843.zip