I am a member of “Generation X”, meaning that I was born in the late 1960’s after the World War II “Baby Boomers”; during my schooling in Latin America I was taught that to answer “not a problem” was impolite and that “you’re welcome” was the better response. Today, that is not necessarily the case; in fact, to answer “not a problem” is the preferred way of answering for “Millennials”, the generation born after the early 1980’s through the early 2000’s.
As a linguist, I can only add that if I have to choose one way over the other, I will always choose “you’re welcome” if the text is polite, the register is high and the target audience is educated and born before 1970. I might choose to use “not a problem” if the audience is younger, or it is an informal reply in a blog.
Sometimes in translation there is not a single right or wrong answer, it all depends on your target audience and whether we want the language to look and feel either “old fashioned” or “avant garde”.