[AssetStore] Unable to complete purchases

I'm trying to buy two plugin, but randomly the site fails. In some cases, immediately after checkout I receive the message:
"A system error has occurred.
We can't find the page you're looking for.
Please contact support to help us fix this issue for you by submitting the error report below.
The system failed to process your request at this time."

When I get to the payment page, I get another error:
"500
Please contact our Customer Service team by submitting a ticket here. Or contact your Sales Representative if your account is managed by our Sales Team. Please provide the following information below by copy. Thank you and we're sorry this happened to you.[ERR:500]"

Is this just my problem??