ETA approved, but only for one day?

Hi everyone! I applied for an ETA today for a flight to the UK in a few weeks and it was pretty much immediately accepted, like within 30 seconds. However, the email I got told me it was only valid for today, the day I applied. I thought they were valid for quite longer than that and am pretty confused, because I was told to apply in advance. Do I need to apply for another one the day of my flight? :( Wondering if any of you have experienced this!! Thank you.