Check that the game directory contains display_mouse_lock_x64.dll;
display_mouse_lock returns whether it could lock the cursor - for example, you cannot lock the cursor when the game window does not have focus (so you might do this in a Step event).
The latest NT build was made with IDE v2024.11.0.179 Runtime v2024.11.0.227 and Steamworks 1.60, so probably the same as yours.