Can't connect to Calbre server on my local Lan.

I can connect to it using local host, but not from other computers or phones on my local LAN, both wireless and wired.
err: this page isn't working right now sent an invalid response

It's not working if I use the full IP address on the host computer (http://192.168.1.135:8080/#library_i...anel=book_list)

Working fine if I use:

http://[::1]:8080/#library_id=Library&panel=book_list

My Ubiquiti router has all local Lan ports open to all local traffic.
My Windows Firewall has Calibre added as a trusted app.

Turned the firewall off, still not working with the full IP address.

Not sure what I'm missing.