Why if a person lit his menorah above 20 amos – he is not yotzah and he is required to make a new Bracha when he relights (M:B 671-29), however if he did not put in enough oil to last 30 min, he also is not yotza but he does NOT have to make a new Bracha (M:B 672-4)- Why? (Mishna breura)
You are asking a nice question. When the Mishna Berura 672-4 says that if less than the correct amount of oil was put in that we don’t say the bracha again, even though we do have to relight the candles, his source is the Chayei Adam 151-21 who says this. See Nishmas Adom 151-1 that explains the reason for this, because there is controversy among the rishonim if we are required to put in a half hour worth of oil or not. We pasken that we have to, however since it is a machlokes, we don’t say the bracha again. In contrast, everyone holds that when the menorah was put above 20 amos that the person is not yotza, therefore when he relights it again he will make a bracha.
NIshmas Adam 151-1