Problem with ionic framework How can I solve?

I am trying to create a pop-up alert using the ionic ion-alert framework and associate it with a button. The problem is that when I press the button, nothing happens and I don’t get any errors.

Full code .ts:

import { Component, OnInit } from '@angular/core';
import { PostProvider } from '../../providers/post-provider';
import { AlertController } from '@ionic/angular';


@Component({
  selector: 'app-tab2',
  templateUrl: './tab2.page.html',
  styleUrls: ['./tab2.page.scss'],
})
export class Tab2Page implements OnInit {
  
  customers: any = [];
  constructor(
    private postPvdr: PostProvider,
    public alertController: AlertController,
  ) { }

  ngOnInit() {
  }

  async presentAlertMultipleButtons() {
    const alert = await this.alertController.create({
      cssClass: '.my-custom-class',
      header: 'Alert',
      subHeader: 'Subtitle',
      message: 'This is an alert message.',
      buttons: ['Cancel', 'Open Modal', 'Delete']
    });

    await alert.present();
  }

  
  loadCustomer(){
    return new Promise(resolve => {
        let body = {
            aksi : 'getCompanyInfo',
        };

        this.postPvdr.postData(body, 'proses-api.php').subscribe(data => {
            for(let company of data.result){
                this.customers.push(company);
            }
            resolve(true);
        });
    });
  }

}

ion-alert is presentAlertMultipleButtons()

Html code:

<ion-content [fullscreen]="true">
  <ion-header>
    <ion-toolbar class="toolbar1">
      <ion-buttons slot="start">
        <ion-menu-button class="icon_menu" autoHide="false"></ion-menu-button>
      </ion-buttons>
    </ion-toolbar>

  </ion-header>

  
  <ion-button expand="full" color ="primary" (click) = "presentAlertMultipleButtons()">
    Pop Up </ion-button> 
</ion-content>

I have compiled in apk and when I press the button it does nothing, but if I press it many times in a row it gets blocked and a part of the pop-up appears:
Image APK

When I get complicated I get this message in the console:Console Message

EDIT: By browsing elemeno, I have found that it works fine, but I think the alert is below the white background. Does anyone know how to correct it?
Inspect Element