Why doesn't the Plotly Dash web application work on the server, but it works on the local machine?

Question

Flask

There is a small web application written in Dash Plotly (which combines Flask and React), the application runs on a local machine, runs on a CentOS server, but when you try to open the application from a link in the browser (I tried it in Chrome, Edge), the application ends on the Loading screen .

The code:

from libs.initsetup import InitSetup
import libs.dbops as dbops
import os
import dash
import dash_core_components as dcc
import dash_html_components as html
from flask_caching import Cache
from flask import Flask

on_server = True

if not on_server:
    WORKDIR = ""
else:
    WORKDIR = "/var/www/mosregwebsite_dash_plot"


external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.cs']
server = Flask(__name__)

dash_app = dash.Dash(__name__, external_stylesheets=external_stylesheets, server=server)

dash_app.scripts.config.serve_locally = True
dash_app.css.config.serve_locally = True

cache = Cache(dash_app.server, config={
    'CACHE_TYPE': 'filesystem',
    'CACHE_DIR': WORKDIR + os.path.join(os.getcwd(), 'cache-directory')
})

TIMEOUT = 1800  # plots are updated every 30 minutes


@cache.memoize(timeout=TIMEOUT)
def return_layout():
    clients = InitSetup.read_initfile_json(WORKDIR + os.path.join(os.getcwd(), "jsons", "clients.json"))
    HOST, DBUSER, DBPASSWORD, AUTH_PLUGIN, *rest = InitSetup.read_mysql_init_config_file(WORKDIR +
        os.path.join(os.getcwd(), "mosregwebsite_dash_plot.config.txt"))

    conn, curs = dbops.create_mysql_connection(HOST, DBUSER, DBPASSWORD, AUTH_PLUGIN)

    graphs = []
    for k, v in clients.items():
        x, y = dbops.select_data_for_pictures(curs, k)
        graphs.append({'x': x, 'y': y, 'type': 'lineplot', 'name': v})

    return html.Div(children=[
        dcc.Graph(
            style={
                'textAlign': 'center',
                'height': '900px',
            },
            id='example-graph',
            figure={
                'data': graphs,
                'layout': {
                }

            }
        )
    ])


dash_app.layout = return_layout

if __name__ == '__main__':
    if not on_server:
        dash_app.run_server(host='127.0.0.103', port=8999, debug=False)
    else:
        HOST, PORT = InitSetup.read_website_settings_from_config_file(
            WORKDIR + os.path.join(os.getcwd(), "mosregwebsite_dash_plot.config.txt"))
        dash_app.run_server(host=HOST, port=int(PORT), debug=False)

Errors that the browser shows: