Exactly! That is why you are rate limited. The invoice rate limit is what you had reached because if you refresh the invoice page too much it'll rate limit you. Then it'll prevent connection too is what I've seen. Happened to me once too because I was developing (theming) the invoice page and I had to refresh a lot and it occurred. Usually, the idea is that once someone pays on the invoice page we don't expect anyone to use it again much.