I already tried it in the FAQ but never got an answer, so I will try it here:

I purchased ARI Fancybox and ARI Cloud Carousel Pro in May. I have written to the 2Checkout Support about an invoice and they answered, that I must ask for an invoice at ARI Soft. After this, I already wrote to the ARI Soft Support about my invoice two or three times, but I never got an answer. So, where can I get my invoice?

Hello,

Sorry for the delay. It seems the mail from our primary address with invoices was blocked. We re-sent it from our secondary address. Check your e-mail please.

Regards,
ARI Soft