I just checked again, and it tells me “no updates found”.
OS Version: 188.8.131.52-prerelease
Build Number: eng.worker.20151230.195810
Build Identifier: 20151230201227
Update Channel: dogfood
Git Commit Info: 2015-12-22 02:20:26
I think I remember having a very big update (190 or 290Mb, can’t remember) maybe one or two weeks ago (I was surprised by the size), does that have anything to do with this lacking update?