Deployment error. Failed to deploy stack - connection refused

Trying to install Nextcloud in docker and I get Deployment error. Failed to deploy stack - connection refused. What to do? Please help!

I also tried as a test this by installing an OpenMediaVault plugin:

The stack looks like:

version: "3"
services:
  nextcloud:
    image: lscr.io/linuxserver/nextcloud:latest
    container_name: nextcloud
    environment:
      - PUID=1000 
      - PGID=100  
      - TZ=Europe/Berlin
    volumes:
      - /files/dev-disk-by-uuid-834cd9ab/nc/nextcloud/config:/config 
      - /files/dev-disk-by-uuid-834cd9ab/nc/nextcloud/data:/data     
    depends_on:
      - mariadb
#    ports: # uncomment this and the next line if you want to bypass the proxy
#      - 450:443
    restart: unless-stopped
  mariadb:
    image: ghcr.io/linuxserver/mariadb
    container_name: nextclouddb
    environment:
      - PUID=1000 #change PUID if needed
      - PGID=100  #change PGID if needed
      - MYSQL_ROOT_PASSWORD=mariadbpassword  #change password
      - TZ=Europe/Berlin
    volumes:
      - /files/dev-disk-by-uuid-834cd9ab/nc/nextclouddb:/config    
    restart: unless-stopped
  swag:
    image: linuxserver/swag         
    container_name: swag
    cap_add:
      - NET_ADMIN
    environment:
      - PUID=1000 
      - PGID=100  
      - TZ=Europe/Berlin
      - URL=mysite.duckdns.org
      - SUBDOMAINS=www,
      - VALIDATION=duckdns
      - DUCKDNSTOKEN=mytoken
      - EMAIL=myemail@mail.com
    volumes:
      - /srv/dev-disk-by-label-disk1/appdata/swag:/config
    ports:
      - 443:443
      - 80:80
    restart: unless-stopped

Update: I filled the DNS settings in OMV because I had static IP set on OMV. Now I get this error after deploying the stack: “This stack was created outside of Portainer. Control over this stack is limited.”