Hi Sam, sorry to learn that you're having some trouble with your TWA.
The first thing to check is the preamp battery in your guitar. Start with a new battery in the guitar and double check to see if your guitar is passing signal. If you have an external amplifier, please plug your guitar in directly to check.
The next step is to try a different instrument cable between TWA and the guitar.
If nothing then, try clicking the parameters and amplitude knobs simultaneously. You'll access the DI menu on screen. If it shows anything besides 'TWA and DI', scroll using the parameters knob until it does and click to confirm.
If you continue to have trouble, shoot us an email at firstname.lastname@example.org and we'd be happy to help!