This problem is constant in D5 Render. Asset loading takes too long and even after several minutes it finishes loading but there is no asset content (even though many are already stored on my SSD). I anticipate to comment that the internet connection or the speed has nothing to do, since I monitor it all the time, and while D5 tries to load content, the internet remains stable.
Hi mate, If the problem still persists, please refer to this blog for solutions. Hope it helps.
[Hot issue] Assets loading and downloading problem - Get Help - D5 RENDER FORUM