When I go to update apps in the store, it downloads them, but as its installing, it quits and gives an error code (80073cf9). Note: I a using a Lumia 521 and with WP10 TP. Thanks
Usually it is either slow WiFi or a sync error in your Microsoft Account.
Let's talk about sync error. Can you sync your Microsoft Account?
Is the date and time correct? Take it off "set automatically" and adjust it forward a couple of years. Soft Reset. Then correct the date and time manually. Soft Reset.