I think you inputted a katakana ニ rather than a kanji 二 , and that’s why it didn’t work.
I went through something similar as well, so I’m going to assume you’re making the same mistake I was. Please correct me if I’m wrong!
It looks like you’re using an Android device, and I’m going to guess that you’re using Google Keyboard / GBoard with either the ‘Japanese QWERTY’ input or the ‘Google Japanese’ input.
I’m also going to guess that you are inputting by typing in the hiragana (or the romaji which gets converted to hiragana as you type), and that after you’ve typed in the full hiragana for the word, you then look in the suggestion box that comes up and pick the one you want?
Doing that doesn’t find what you want half the time. Rather than giving you words that match exactly the hiragana you’ve typed out, it gives you suggestions on words it thinks you might want to type out based on the hiragana you’ve put in. Kind of like predictive text.
You need to press the spacebar first, then pick out the correct kanji from the suggestion box. Pressing space limits the suggestions in the box to actual words that match what you’ve put in. That makes it much easier to find what you’ve actually typed rather than wading through a billion suggestions.