Sorry if im putting this in the wrong forum. Im not asking for payment support, just giving you my perspective on something that could be an issue.
Since ive been a satisfied user of Avast Home for a long time now I felt it only right that I show my support and buy the proffessional edition. I tried doing so and immediately received a payment confirmation, as usual for online shopping, as if all was well. But then the next morning I see an unspecific mail that basically just says "payment failed". Something similar has happened a total of once during my many years of buying things over the internet and this does not create a good impression. I even doublechecked my details to make sure there was no mistake on my end but since there werent I saw no reason to try again.
I might still go for a local purchase option, even though its costs a bit more. However a person in my situation thats just buying to show support and doesnt really care much about the additional features will, in my opinion, be very likely to just say "forget it" and keep using the home edition. And thus the point of the post: if this happens frequently, and I didnt just get unlucky somehow, you might want to consider if its costing you sales and perhaps use another payment system.