Embedder fails to load

import {
    ChangeDetectionStrategy,
    Component,
    ElementRef,
    ViewChild
} from '@angular/core';

@Component({
    template: `
        <button *ngIf="!embedderRef" (click)="mount()">Mount</button>
        <button *ngIf="embedderRef" (click)="unmount()">Unmount</button>
        <div class="full-height">
            <span #dropboxEmbed></span>
        </div>
    `,
    changeDetection: ChangeDetectionStrategy.OnPush
})
export class DropboxIntegrationComponent {
    private loadAPI: Promise<any>;
    public embedderRef: any;

    private appkey = '';
    private shareLink = '';

    @ViewChild('dropboxEmbed', {static: true})
    public dropboxEmbed: ElementRef;

    constructor() {
        this.loadAPI = new Promise((resolve) => {
            const node = this.loadScript('dropboxjs', 'https://www.dropbox.com/static/api/2/dropins.js', [{
                name: 'data-app-key',
                value: this.appkey
            }]);
            if (node) {
                node.onload = () => {
                    resolve(true);
                };
            } else {
                resolve(true);
            }
        });
    }

    public mount() {
        this.embedDropboxView();
    }

    public unmount() {
        const dropboxObject: any = window[<any>'Dropbox'];
        if (this.embedderRef && dropboxObject && dropboxObject.unmount) {
            dropboxObject.unmount(this.embedderRef);
            this.embedderRef = undefined;
        }
    }

    private embedDropboxView() {
        const options = {
            link: this.shareLink,
            file: {
                zoom: 'best'
            },
            folder: {
                view: 'list',
                headerSize: 'normal'
            }
        };

        const dropboxObject: any = window[<any>'Dropbox'];
        if (dropboxObject && dropboxObject.embed) {
            this.embedderRef = dropboxObject.embed(options, this.dropboxEmbed.nativeElement);
        }
    }

    private loadScript(id: string, src: string, customAttributes: {name: string, value: string}[]) {
        let isFound = false;
        const scripts = document.getElementsByTagName('script');

        for (let i = 0; i < scripts.length; ++i) {
            const f = scripts[i].getAttribute('id');
            if (scripts[i].getAttribute('id') == id) {
                isFound = true;
            }
        }

        if (!isFound) {
            const dynamicScript = src;
            const node = document.createElement('script');
            node.src=dynamicScript;
            node.type = 'text/javascript';
            node.async = false;
            node.id = id;

            customAttributes.forEach(attr => node.setAttribute(attr.name, attr.value));

            document.getElementsByTagName('head')[0].appendChild(node);
            return node;
        }

        return undefined;
    }
}