Android signed/ unsigned both .apk file is keep stopping

Question

I convert a website in an android app using web view but it keeps stopping in my client mobile. His phone is morto E4 his API level is 25 and I set min SDK of app 21 and max is 29. I don't understand the issue. It's working fine in my phone and I also test in 3 more phones it's working. Following is my code and everything I use in my code. kindly help me i don't upload logo of my app if required I'll do that.

Gradle-app

    enter code here
apply plugin: 'com.android.application'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.3"

    defaultConfig {
        applicationId "com.farah.tawaqqo"
        minSdkVersion 21
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'

}

main activity

    enter code here

package com.farah.tawaqqo;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.app.ProgressDialog;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.Network;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.webkit.WebChromeClient;
import android.webkit.WebResourceRequest;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.RelativeLayout;
import android.widget.Toast;

import com.farah.tawaqqo.Common.Common;

import java.net.ConnectException;

public class MainActivity extends AppCompatActivity {

    WebView webView;
    ProgressBar progressBar;

    ProgressDialog progressDialog;

    private String url = "https://tawaqqo.com/";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        webView = (WebView) findViewById(R.id.webView);
        progressDialog = new ProgressDialog(this);


        if (Common.isConnectedInternet(getBaseContext())) {

            // progressDialog.dismiss();
            WebSettings webSettings = webView.getSettings();
            webView.getSettings().setDomStorageEnabled(true);
            webView.getSettings().setJavaScriptEnabled(true);
            webSettings.setJavaScriptEnabled(true);
            webView.loadUrl(url);
            webView.setWebViewClient(new WebViewClient());
        } else {
            //  progressDialog.dismiss();
            progressDialog.setTitle("Internet Issue");
            progressDialog.setMessage("Please connect to wifi.");
            progressDialog.setCanceledOnTouchOutside(false);
            progressDialog.show();
        }

       progressBar = (ProgressBar) findViewById(R.id.progressBar);


        webView.setWebChromeClient(new WebChromeClient() {
            @Override
            public void onProgressChanged(WebView view, int newProgress) {


                progressBar.setVisibility(view.VISIBLE);
                progressBar.setProgress(newProgress);

                setTitle("Loading.....");
                if (newProgress == 100) {
                    progressBar.setVisibility(view.GONE);
                    setTitle(view.getTitle());
                }
                super.onProgressChanged(view, newProgress);
            }
        });

    }


    @Override
    public void onBackPressed() {

        if (webView.canGoBack()) {
            webView.goBack();

        } else
            super.onBackPressed();
    }
}

splash activity

    enter code here

package com.farah.tawaqqo;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.Window;
import android.view.WindowManager;

public class Splash extends AppCompatActivity {

    Handler handler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);

        handler=new Handler();
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                Intent intent=new Intent(getApplicationContext(),MainActivity.class);
                startActivity(intent);
                finish();
            }
        },3000);
    }
}

**Common class for internet connection**

    enter code here
package com.farah.tawaqqo.Common;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;

public class Common {

    public static boolean isConnectedInternet(Context context)
    {
        ConnectivityManager connectivityManager = (ConnectivityManager)context.getSystemService(context.CONNECTIVITY_SERVICE);
        if(connectivityManager != null)
        {
            NetworkInfo[] info = connectivityManager.getAllNetworkInfo();
            if( info != null)
            {
                for(int i=0;i<info.length;i++)
                {
                    if(info[i].getState() == NetworkInfo.State.CONNECTED)
                        return true;
                }
            }
        }
        return false;
    }
}