I totally understand how you're feeling! I used to have a traditional pay as you go meter before switching to a credit meter, so I can relate. It sounds like Blastoise is on the right track as there might be an issue with the serial number of your key not matching, but that seems unlikely if it has worked for you before. It’s more likely that your meter is having some trouble and might need a replacement.
To make sure it's not the key, you can check for nearby shops that have keys available by using your post code on https://www.paypoint.com/instore-services/energy-top-ups. That way, you can pick up a new one if needed!
I’d suggest reaching out to our pay as you go support team. Just let them know you’re getting an error code on your meter and that you need an emergency exchange. They’re really helpful and usually sort out emergencies on the same day to keep things running smoothly for you.
When you do get the meter exchanged, it will be replaced with a smart meter. This means you’ll have more control over your usage. You can either stay on credit so you won’t have to stress about running out of supply or go for the smart pay as you go option, which lets you top up right from an app instead of trekking to a shop.
I really hope this helps, and that everything gets sorted out quickly! If you have any more questions, feel free to ask! 😊