NCAA-W substitution

[Forksref]

I was watching NCAA-W game on Saturday. One team called a TO. I don't remember which team. Near the end of the TO, while both teams were still huddled, a player was at the table, having checked in to sub. At the end of the TO, one official told the player that they couldn't come into the game. They had to wait for the next dead ball. Anyone familiar with this? If it was interpreted wrong or even if the official was right, it doesn't make sense.