Hi Paul. Welcome to justanswer.
What happens when you try to turn on wifi. Do you get any error?
Okay. Press the power off button so that the option to POWER OFF appears on the screen. When it does, touch and HOLD power off option on the screen so that a message to REBOOT IN SAFE MODE appears. Select it. Now the tab will restart. When it turns on, check if still the wifi is not working?
Try it and then update me
Does your tab have SideSync app?
Go to Settings-Apps. Find SideSync from the list and tap UNINSTALL UPDATES and then restart the tab
See if this works else we will have to enter into recovery mode.
Paul, your Bluetooth is turned off right?
Okay then turn it off.
When tab is completely off, Press and hold the Volume Up button, the Home button and Power button and continue holding all three buttons until Recovery Booting appears in the upper left.
Once the Recovery Menu appears, You may release all buttons.
Using the Volume Down button, highlight ‘wipe cache partition’ and press the Power button to select it.
After the wipe is complete, choose ‘reboot system now’ and press the Power button to restart the tablet.
Now reboot as stated above.
Go to Settings. Do you see About tab. Tap it and then select Check for updates.
Do you have an active mobile internet ?
Connect your tab to the computer and try updating via Kies
Once you click the link(http://www.justanswer.co.uk/remotedesktop/join.aspx?Session=aa5ce6fe-c6af-420f-a839-60b78ba38fb0)You will be redirected to a page. Press I Agree and a file will automatically get downloaded. Check your download section, a file named ELSINORE.SCREENCONNECT will be present. Just open that file so that I can connect to your computer.