Why is the CAPIT Highlighter Not Working?

My student is highlighting all the letters but the app is saying it's wrong!

Our Spelling Cards contains a Highlighter Interface. It asks students to segment a word into separate sounds (i.e. phonemes) using colors. The key here is that students must separate the word into separate SOUNDS, not LETTERS. So, although the word "cat" has 3 sounds and 3 letters, words like "off" and "egg" which have 3 letters get only 2 colors because they have only 2 sounds, and words such as "mess" and "duck" which have 4 letters get only 3 colors because they have only 3 sounds.

Our Highlighter Interface prepares beginner students for dealing with the more complicated digraphs and diphthongs (e.g. sh, ch, oo, oi).