For the last couple of days (up to and including 21 Feb 2016) I'm unable to upload an Application logo on the settings pages of the apps listed on my https://account.live.com/developers/applications/index
On "basic information" of the "edit settings" page, I can select the "Application logo" using the button (browsing and selecting a file); and it shows the filename. However, when I click "Save" it appears that the file is uploaded, but not properly processed, as the logo is NOT updated.
I'm pretty sure it is uploaded, because the dimensions are checked (it complains about a 192x192 logo for example, but accepts a 48x48 one); but it just doesn't store it.
When I save using the 48x48 logo, it shows "Your changes were saved" in green (but the logo isn't updated, still empty; also when I go to the overview page). When saving with a 192x192 logo, it shows "The logo must be 48 by 48 or 50 by 50 pixels" for the "Application logo" field (and there is no success message, as expected).
"Microsoft account Developer Center" seems to be broken - there is quite a few things that doesn't work there - not only the logo upload.
I recommend everyone to use https://apps.dev.microsoft.com/#/appList instead. It has slightly different UI but all the data from the previous one is also visible there and logo upload just works.