I’m guessing this who you meant to tag :)

nostr:npub1s33sw6y2p8kpz2t8avz5feu2n6yvfr6swykrnm2frletd7spnt5qew252p

If you’re unfamiliar with tagging - you type the @ symbol, followed by their name (without a space before the name)

So I typed “@“ and then immediately “Matth” and by then his account showed up for me to select. I follow him already so it was easy. You could also type “@ followed by BitcoinUniversity to pull his account up for tagging.