Zigbee2mqtt web ui not loading devices

Hi,

I have a HomeAssistant setup running on a RPi with zigbee2mqtt add-on configured, and everything was working fine.

Recently I added a reverse-proxy (Nginx Proxy Manager) to my network (running in a docker container on a separate machine) and configured so that I can access my HA instance through my domain name. Seemed to be working fine, but I just noticed, that when I open the Web UI for Zigbee2Mqtt add-on, the list of devices, map, setting, etc are empty. Note that the integration itself is till working, so I can control the devices that I already added to HA.

I assume that adding the reverse-proxy to the mix broke something in the UI, but I’m not sure if I need to configure something in the Zigbee2Mqtt integration, or on the Nginx Proxy Manager to get the UI working again fine.

Does someone has similar setup and made it work, or know what is the issue and how to fix it?

Here’s some more info about my configurations:
Zigbee2Mqtt add-on configuration:

data_path: /config/zigbee2mqtt
socat:
  enabled: false
  master: pty,raw,echo=0,link=/tmp/ttyZ2M,mode=777
  slave: tcp-listen:8485,keepalive,nodelay,reuseaddr,keepidle=1,keepintvl=1,keepcnt=5
  options: "-d -d"
  log: false
mqtt:
  base_topic: zigbee2mqtt
  server: mqtt://core-mosquitto:1883
  user: <user>
  password: <password>
serial:
  disable_led: true
  port: /dev/ttyUSB0
external_converters: []
devices: devices.yaml
groups: groups.yaml
homeassistant: true
permit_join: true
device_options: {}
blocklist: []
passlist: []
queue: {}
frontend:
  port: 8099
experimental: {}
availability: false

Nginx Proxy Manager settings:

## Proxy Host:
### Details
 - Domain names: hass.mydomain.com
 - Scheme: HTTP
 - Forward Hostname / IP: local.ip.to.pi
 - Forward Port: 8443
 - Block Common Exploits: Enabled
 - Websocket support: Emabled
### Custom Locations
 - Location: \
 - Scheme: HTTP
 - Forward Hostname / IP: local.ip.to.pi
 - Forward Port: 8443
 - Additional options:
   - proxy_set_header Upgrade $http_upgrade;
   - proxy_set_header Connection “upgrade”;
### SSL
 - Force SSL: Enabled
 - HTTP/2 Support: Enabled