Is there any penalty for not showing up to your train?

I have a trip booked with South Western Railway in the morning but I am not feeling well. I booked it online and have a rail card. I don’t see an option to cancel on the app. The ticket was pretty cheap, so I don’t care about a refund. I am just wondering if there are any consequences for not showing up for my train? I don’t want to lose my rail card or get charged a fee.