IOS - WebView - "Hide My IP" and "PopUp"

I have the following situation: I am trying to access a page that I can only access after we have logged in with the Microsoft 2FA auth. I always got the same error "415 Unsupported Media Type" in the Safari browser. After I had deactivated "Block POP" in the Safari settings and set "Hide my IP" to OFF, everything worked fine in the Safari browser.

Now I am trying the same thing in my app in the WebView. I have already tried this code:

import UIKit
import SafariServices

class HorizonViewController: UIViewController, SFSafariViewControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        showWebPage()
    }

    func showWebPage() {
        if let url = URL(string: "https://myurl") {
            let safariVC = SFSafariViewController(url: url)
            safariVC.delegate = self
            self.present(safariVC, animated: true, completion: nil)
        }
    }

    // Optional: SafariViewController Delegate Methoden
    func safariViewControllerDidFinish(_ controller: SFSafariViewController) {
        // Wird aufgerufen, wenn der Benutzer den SafariViewController schließt
        controller.dismiss(animated: true, completion: nil)
    }

    // Sie können hier weitere Delegate-Methoden hinzufügen, falls Sie sie benötigen.
}

an also this code:

import UIKit
import WebKit

class HorizonViewController: UIViewController, WKNavigationDelegate, WKUIDelegate {

    var webView: WKWebView!

    override func loadView() {
        // Erstellen einer Web-Konfiguration
        let webConfiguration = WKWebViewConfiguration()
        
        // Deaktivieren des Cross-Site-Trackings
        webConfiguration.websiteDataStore = WKWebsiteDataStore.nonPersistent()

        // Erstellen der WebView mit der obigen Konfiguration
        webView = WKWebView(frame: .zero, configuration: webConfiguration)
        
        webView.navigationDelegate = self
        webView.uiDelegate = self
        view = webView
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        if let url = URL(string: "https://glavid.golav.lu/") {
            var request = URLRequest(url: url)
            request.setValue("application/json", forHTTPHeaderField: "Accept")

            webView.load(request)
        }
    }

    // MARK: - WKNavigationDelegate
    // Optional: Hier können Sie die Navigation im WebView steuern

    // MARK: - WKUIDelegate
    func webView(_ webView: WKWebView, createWebViewWith configuration: WKWebViewConfiguration, for navigationAction: WKNavigationAction, windowFeatures: WKWindowFeatures) -> WKWebView? {
        if navigationAction.targetFrame == nil {
            webView.load(navigationAction.request)
        }
        return nil
    }
}

Unfortunately, I get the same error 415 after the 2FA.