I always go to mathoverflow.net rather than mathoverflow.net/questions, because the latter only shows 50 results per page including results in tabs you've hidden (so I only see about 4 per page). Normally the former option displays loads of questions ( always a superset of those in the question tab). However, it seems the former is no longer displaying questions at all. Have others noticed this too? Is this by design?
This was unexpected fallout from a change that was intended to limit the impact of requests with an excessively large list of tag criteria. The issue related to a very large number of ignored tags (331) with the "hide ignored tags" preference enabled. I have revised the limits while I investigate further. Sorry for any disruption.