Error While loading app on Browser version5.0

I am trying to run traccar5.0 through source code but getting below error although previous version was running without any error.
When I run npm start, I get below error.

./src/map/core/Map.js 173:32
Module parse failed: Unexpected token (173:32)
You may need an appropriate loader to handle this file type.
|   var locationIqKey = useAttributePreference('locationIqKey', 'pk.0f147952a41c555a5b70614039fd148b');
|   var customMapUrl = useSelector(function (state) {
>     return state.session.server?.mapUrl;
|   });
|   useEffect(function () {

Please help to resolve this error.

It's not Traccar 5.0. It looks like you changed some code and it complains about your changes.

My app is running and compiled successfully But on browser it shows this :
Unable to connect

Firefox can’t establish a connection to the server at localhost:3000.

The site could be temporarily unavailable or too busy. Try again in a few moments.
If you are unable to load any pages, check your computer’s network connection.
If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web.

What is the solution for this?

Sir I addressed the above issue again what I have to do to solve it?