I have recently discovered some mistakes in a published maths article. I have contacted the author pointing out politely my concerns, but I got no specific answer, just a "polite" one, that the aspects I am addressing are clarified in some of his other papers (without mentioning which are these papers). Although my remarks where specific and could have been answered with a simple counter-argument (if there was any), the author avoided a direct answer. What is also concerning is that these errors are "copied" by others who base their research on this published paper.
My question is how do you signal these errors to the community? What is the right process if the authors avoids to take credit?