We currently only support word, sentence and paragraph text selections (and from there copying and highlighting). The scenario you're describing should definitely work. If you try another location, then go back to that one will it work? If not, can you tell us which resource and exact location you're attempting?
Trying in multiple locations, same results everywhere. I can't select anything but one word. If I tap a word and release, I see a choice of selecting word, sentence, or paragraph. If I tap sentence, I get a color selection box (but the sentence is not selected in any visible way); if I tap a color, the selection box disappears but nothing is highlighted. However, if I tap "word" instead of sentence, and follow the above steps, the single word does get highlighted. This is in the REB.
In the ESVS, when I tap a word and release, it goes at once to a selection of "copy, highlight, search, amplify". I tap "highlight" and it give me color selection; tap a color, and the word gets highlighted. I cannot find any way to select a sentence or paragraph, and I do not get offered the choice for that when in ESVS. KJVS gives me the same results.