Do you see the Firefox window or is that hidden?

You can try to open the system menu via Alt+Space and try to use the move and resize commands to move the window into view and possibly maximize the window.

bdsd said

I have tried re intalling it, but when i click on the Icon it comes up on the taskbar but will not maximize.

did not work

You may have a corrupt xulstore.json file. https://support.mozilla.org/en-US/kb/changes-toolbars-and-window-sizes-are-not-saved

This is a more detailed explanation of the previous suggestions.

Sometimes a window gets "off screen" somehow. You often can force it to appear on the screen by right-clicking the little thumbnail image above the Taskbar and choosing Maximize. Does that work?

One possible cause for this is that the file which stores window sizes and positions has become corrupted.

Method #1: If you can get a maximized window:

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename xulstore.json to something like xulstore.old. If you see a file named localstore.rdf, rename that one to localstore.old.

Start Firefox back up again. Do windows display normally again?

Method #2: If you cannot get a Firefox window at all:

Shut down Firefox by right-clicking the taskbar icon > Close All Windows.

Using the Run dialog (windows key + R) or the Start menu search bar (or in Windows 8.1 maybe the charms bar search bar?) type or paste the following and press Enter to drill down to the Profiles folder:

%APPDATA%\Mozilla\Firefox\Profiles

Here you may see one folder -- in which case, double-click into that -- or more than one folder -- in which case, double-click into what looks like the most recently updated.

Scroll down and rename xulstore.json to something like xulstore.old. If you see a file named localstore.rdf, rename that one to localstore.old.

Start Firefox back up again. Do windows display normally again?

bdsd said

I have tried re intalling it, but when i click on the Icon it comes up on the taskbar but will not maximize.

Found the problem,I have two monitors but was not using one of them but firefox was open in the other monitor, problem fixed ,kinda of dumb eh.

Hi bdsd, I wouldn't have guessed that, so it's great that you thought of it. Does Windows have a way to switch your view, so if you're only have one monitor turned on you can quickly see what's on the other one by switching the screens between them? That would be handy...

That was very good work. Well Done. Please flag your last post as Solved Problem so other will know.