Unable to setup gokapi on a NAS - "Server is in maintenance mode, please try again in a few minutes."

[pk-1966]

I have deployed a gokapi container, but when I try to enter setup, I just get a "Server is in maintenance mode, please try again in a few minutes." browser page displayed.

I am running docker (container manager) on Synology DSM, managed using Portainer to run a variety of applications and wanted to set up gokapi as an alternative to FileBrowser.

Portainer uses 'stacks' which are equivalent to docker-compose - here is the stack/compose file

services:
  gokapi:
    image: f0rc3/gokapi:latest
    container_name: gokapi
    ports:
      - "14012:53842"
    volumes:
      - /volume1/transfers/gokapi:/app/data
      - /volume1/apps/gokapi:/app/config
    networks:
      - mediatools
    environment:
      - TZ=Europe/London
      # ID Lengths
      #- GOKAPI_LENGTH_ID=15
      #- GOKAPI_LENGTH_HOTLINK_ID=40
      # App Directories
      #- GOKAPI_CONFIG_DIR=config
      #- GOKAPI_CONFIG_FILE=config.json
      #- GOKAPI_DATA_DIR=data
      # Chunk & Upload Config
      #- GOKAPI_CHUNK_SIZE_MB=45
      #- GOKAPI_MAX_FILESIZE=102400
      #- GOKAPI_MAX_MEMORY_UPLOAD=50
      #- GOKAPI_MAX_PARALLEL_UPLOADS=4
      #- TMPDIR=/app/data/tmp
      # Other flags
      #- GOKAPI_DISABLE_CORS_CHECK=false
      - GOKAPI_LOG_STDOUT=true
      #- GOKAPI_ENABLE_HOTLINK_VIDEOS=false
      #- DOCKER_NONROOT=false
    restart: unless-stopped
networks:
  mediatools:
    name: mediatools
    external: true  

I made some tweaks to the compose file to align with my conventions/standards/situation

• I have removed the 127.0.0.1 from the port mapping (because I am connecting from a PC) (I also tried "0.0.0.0:" before the port)
• I adjusted the port number to 14012 (although have tried the standard port 53842 too)
• I used folder binds rather than docker volumes
• I moved the environment variables from the .env file to directly within the compose file (leaving them commented out until I need to adjust them)

The container starts OK - here is the console log

2025-07-15T09:39:26.406845598Z 
2025-07-15T09:39:26.407490234Z ██████   ██████   ██   ██  █████  ██████  ██ 
2025-07-15T09:39:26.407569344Z ██       ██    ██ ██  ██  ██   ██ ██   ██ ██ 
2025-07-15T09:39:26.407608659Z ██   ███ ██    ██ █████   ███████ ██████  ██ 
2025-07-15T09:39:26.407642631Z ██    ██ ██    ██ ██  ██  ██   ██ ██      ██ 
2025-07-15T09:39:26.407684548Z  ██████   ██████  ██   ██ ██   ██ ██      ██ 
2025-07-15T09:39:26.407718961Z                                              
2025-07-15T09:39:26.407752140Z Gokapi v2.0.1 starting
2025-07-15T09:39:26.408228507Z Please open http://127.0.0.1:53842/setup to setup Gokapi.

The folder mappings work OK because I have connected to a shell (sh) in the container and 'touch'ed files in /app/data and /app/config and both appeared in the external folder. No gokapi files have yet been created in the folder.

The environment variables I have set do appear when I run 'env' under sh.

Any other pointers on what I need to do to get it running?