Ionic Capacitor Firebase Can't get video to work

Hoping you can help? I am trying to create an app for my club. The idea is to store tutorial videos on Firebase storage and then call them as and when they are needed. I have been going round in circle for about a week now. I can get the player to work fine with a generic URL but as soon as I substitute it for the URL from firebase I get an error.
GET http://localhost:8100/[object%20Promise] net::ERR_ABORTED 404 (Not Found)
Uncaught (in promise) DOMException: Failed to load because no supported source was found.
Any ideas where I’m going wrong?

this.res =‘Poomsae’).child(‘Poomsae1K.mp4’).getDownloadURL().then(res => console.log(res));
this._videoPlayer.initPlayer({mode: ‘fullscreen’, url: this.res});