Photoshop CC 2017 is not allowing me to resize images or canvases. The tool boxes open when I click the menus, but then I can't enter anything in the value boxes. It makes things pretty difficult when you're trying to do graphics.
Are you using the Image Size dialog accessed via Image > Image Size? In that dialog, is the Resample box checked? It needs to be if you want to actually change the size rather than monkey with the resolution.