AssetBundels wont work on some browsers or computers

Hi.

I have a system built where i can download assetbundles. It is working on my firefox browser but its not working on my safari browser. On my friends computer it is working on all different browsers. In my home computer its not working at all. It all seems kind of random to me. Why is it that on some computers the bundles get loaded all the time and on other ones they even dont start to download at all, ???