I have done as you suggest twice and removed my add blocker (as an afterthought) and deleted the AD App and reinstalled but still no preview. I have the problem with both iPad and iPhone. There was a recent iOS update and I wonder if this may be the cause.
I am still having this problem on all devices. Previews also fail to appear when visiting the Amazon Drive website using both Safari and Chrome. It is therefore not an iOS issue but an Amazon glitch I think.
Does anyone have any similar experience or suggestions.