Hello, I just installed Inkscape, I'm just trying to get the basics down and trying to use the ellipse and square tool. It was working fine initially but now when I select it and use it nothing shows up. I've changed the fill and stroke colors, but that does nothing. I know this is a rookie question and looked it up on the manual and the forum but could find nothing. Any help would be greatly appreciated. Thanks.

You probably have the opacity set to 0. Open the Fill and Stroke dialogue and see if Opacity slider and/or Alpha box are set to 0.

Welcome to InkscapeForum!

Well, that does seem to happen, lol, I think I recall something similar when I first got Inkscape. There are several possibilities:

-- Have you played with transparency at all? This would be in the Fill and Stroke dialog, the A (alpha) slider, or below that, Opacity. You also might have accessed it in the bottom left corner of the Inkscape window. If you see a zero rather than 100, just to the right of the fille and stroke indication, well, it should be 100.
-- Have you had the Layers dialog open? There's also an Opacity setting for layers.
-- The Ellipse tool also can draw arcs and wedges, and sometimes if it's left in a certain position, you can't see it. Please select the Ellipse tool and draw an ellipse, even if you can't see it. While it's still selected, go to the tool control bar (across top of canvase, above ruler), and click the last button on the right. This will reset it to default (full ellipse/circle).
-- You can do the same thing with the Rectangle tool.

There are other possibilities as well. Are you using a graphics tablet, by chance? (such as Wacom?) And there are still others, but let's start here, and see what develops. Let us know if any of those things fixed it.

Oops, hi prkos, you posted while I was typing!

Your stroke default may be turned off, and since you have to fill it before you can see the box, (or whatever shape you select), you may think that it isn't there, but it may be, that used to happen to me until I re-set Inkscapes Preferences. Inkscape's defaults might be set to 'last used style', you can check it by going to Inkscape Preferences, Shapes, and set it to 'This tool's own style'.
You can check to see if there are rectangles on your work by using the rubberband method (click and drag from the mouse), over your entire work area and if a selection shows up, you can either delete the extra boxes or use them.

It worked! Thank You!!!