Good afternoon should be accepted. Make sure you report it next time you see it so the course creators can add it as an alternative.
It says that it should be translated as "Good morning", well, that would be "Guten Morgen". I think "Good afternoon" should be accepted here.
It told me: Good morning, Ann and Lukas!. Names are not translated!!!
I agree with the others. Good afternoon should be accepted under the following points: 1.) When you click on the phase Guten tag the program itself gives the meaning of good afternoon!!! 2.) Guten morgen is translated as Good morning and Guten tag is translated as good day or good afternoon. 3. ) People even say Guten tag after about 11 am, because Germans get up so early to them half the day is already over!