Unable to purchase addons

Have you tried more than one script to checkout from different developers?

Yes, and it work other addons...

If it worked with others, and not a certain one, then it has something to do with the developer's paypal. He may have a negative balance. So when you make the purchase, it gives him the money, but he may not have enough to cover the gmodstore fee so it denies the entire purchase. You'll have to contact the developer.

Okey thanks Richard :)

Also just as a heads up with this. If you are using a PayPal Balance then PayPal is either blocking their PayPal or their Country due to fraud claims. If the person has a Fraud claim on their account you will be unable to do anything about it. Just message the Creator & ask whats up. Now if your using a Credit or Debit Card i would check with your Bank &/or Card Company as some Banks are blocking payments to certain countries that have been having a lot of Fraud Claims.

I had call PayPal and it say the problem not coming in my paypal but the paypal developer..

Sounds kind of odd that you can't buy Prometheus.

I don't know what could be causing this as I have no outstanding balance and other people can purchase it just fine