"He came yesterday."
Translation:Er kam gestern an.
Not native but this looks right to me. Flag it via the reprt button Sometimes its hard to ensure all permutations of a sentece will all be marked correct for example you could also have written: gestern ist er angekommen. or Er ist gestern angekommen. These are both valid but it takes a lot of work to ensure all are accepted as valid answes, dont stress it too much just report it.