How to fix error 503 after deploy on heroku?

Question

MongoDB

Good afternoon, yesterday I depolized to Heroku, everything is ok, according to the logs there were no errors. But when the application is opened, data from the server is not loaded, an error 503 is issued. I think this is related to the IP address, but I don’t know how to fix it yet. If you can advise something, I will be grateful!)
Link to the Deploy Logs application :

-----> Node.js app detected
       
-----> Creating runtime environment
       
       NPM_CONFIG_LOGLEVEL=error
       NODE_ENV=production
       NODE_MODULES_CACHE=true
       NODE_VERBOSE=false
       
-----> Installing binaries
       engines.node (package.json):  unspecified
       engines.npm (package.json):   unspecified (use default)
       
       Resolving node version 10.x...
       Downloading and installing node 10.16.0...
       Using default npm version: 6.9.0
       
-----> Installing dependencies
       Installing node modules (package.json + package-lock)
       
       > [email protected] install /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/grpc
       > node-pre-gyp install --fallback-to-build --library=static_library
       
       [grpc] Success: "/tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/grpc/src/node/extension_binary/node-v64-linux-x64-glibc/grpc_node.node" is installed via remote
       
       > [email protected] install /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/yorkie
       > node bin/install.js
       
       setting up Git hooks
       can't find .git directory, skipping Git hooks installation
       
       > [email protected] install /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/bcrypt
       > node-pre-gyp install --fallback-to-build
       
       [bcrypt] Success: "/tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/bcrypt/lib/binding/bcrypt_lib.node" is installed via remote
       
       > [email protected] install /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/node-sass
       > node scripts/install.js
       
       Downloading binary from https://github.com/sass/node-sass/releases/download/v4.11.0/linux-x64-64_binding.node
       Download complete
       Binary saved to /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/node-sass/vendor/linux-x64-64/binding.node
       Caching binary to /tmp/npmcache.Y4DPK/node-sass/4.11.0/linux-x64-64_binding.node
       
       > [email protected] postinstall /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/@google-cloud/firestore/node_modules/protobufjs
       > node scripts/postinstall
       
       
       > [email protected] postinstall /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/@grpc/proto-loader/node_modules/protobufjs
       > node scripts/postinstall
       
       
       > [email protected] postinstall /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/google-gax/node_modules/protobufjs
       > node scripts/postinstall
       
       
       > [email protected] postinstall /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/google-proto-files/node_modules/protobufjs
       > node scripts/postinstall
       
       
       > [email protected] postinstall /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/node-sass
       > node scripts/build.js
       
       Binary found at /tmp/build_920b3aea7085334ee21f75f2f31a5e95/node_modules/node-sass/vendor/linux-x64-64/binding.node
       Testing binary
       Binary is fine
       added 1662 packages from 844 contributors and audited 27368 packages in 41.808s
       found 29 vulnerabilities (18 moderate, 11 high)
         run `npm audit fix` to fix them, or `npm audit` for details
       
-----> Build
       Detected both "build" and "heroku-postbuild" scripts
       Running heroku-postbuild
       
       > [email protected] heroku-postbuild /tmp/build_920b3aea7085334ee21f75f2f31a5e95
       > npm run build
       
       
       > [email protected] build /tmp/build_920b3aea7085334ee21f75f2f31a5e95
       > vue-cli-service build
       
       
-  Building for production...
        WARNING  Compiled with 3 warnings1:10:02 PM
       
        warning  
       
       asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
       This can impact web performance.
       Assets: 
         js/chunk-vendors.e5068d64.js (943 KiB)
       
        warning  
       
       entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
       Entrypoints:
         app (1.2 MiB)
             css/chunk-vendors.a5c66230.css
             js/chunk-vendors.e5068d64.js
             css/app.bbc8fdc9.css
             js/app.12e7ec71.js
       
       
        warning  
       
       webpack performance recommendations: 
       You can limit the size of your bundles by using import() or require.ensure to lazy load some parts of your application.
       For more info visit https://webpack.js.org/guides/code-splitting/
       
         File                                   Size              Gzipped
       
         dist/js/chunk-vendors.e5068d64.js      942.89 KiB        320.52 KiB
         dist/js/app.12e7ec71.js                73.28 KiB         16.41 KiB
         dist/css/app.bbc8fdc9.css              206.67 KiB        26.93 KiB
         dist/css/chunk-vendors.a5c66230.css    2.19 KiB          0.75 KiB
       
         Images and other types of assets omitted.
       
        DONE  Build complete. The dist directory is ready to be deployed.
        INFO  Check out deployment instructions at https://cli.vuejs.org/guide/deployment.html
             
       
-----> Caching build
       - node_modules
       
-----> Pruning devDependencies
       
       > [email protected] uninstall node_modules/yorkie
       > node bin/uninstall.js
       
       husky
       uninstalling Git hooks
       done
       
       removed 935 packages and audited 2914 packages in 13.806s
       found 9 moderate severity vulnerabilities
         run `npm audit fix` to fix them, or `npm audit` for details
       
-----> Build succeeded!
-----> Discovering process types
       Procfile declares types     -> (none)
       Default types for buildpack -> web
-----> Compressing...
       Done: 87.9M
-----> Launching...
       Released v6
       https://vue-activity-planner.herokuapp.com/ deployed to Herok