Can't view Word files

Hi, I'm pointing to a Word file (.docx) and it first shows an animation:

Then after about 3 seconds, I get this error:

The browser inspector shows a bunch of network calls, some which succeed and others that fail with a 404. The 404 calls look like this:

- https://pus7-word-view.officeapps.live.com/wv/ResReader.ashx?n=p1.img&WOPIsrc=http%3A%2F%2Fpus7%2Dview%2Dwopi%2Ewopi%2Eonline%2Eoffice%2Enet%3A808%2...
- https://pus7-word-view.officeapps.live.com/wv/docdatahandler.ashx?WOPIsrc=http%3A%2F%2Fpus7%2Dview%2Dwopi%2Ewopi%2Eonline%2Eoffice...

Does anyone know what the problem is? BTW, Excel files (.xlsx) work fine.

Thanks,
Alvaro