WordNet sense 1 (not solved):

unsolved

WordNet sense 2 (not brought to a conclusion; subject to further thought):

open, undecided, undetermined

WordNet sense 3 (still in doubt):

unsettled

WordNet sense 4 (characterized by musical dissonance; harmonically unresolved):

dissonant

WordNet sense 5 (not in harmony):

inharmonious, unharmonious