In the OS, at mouse driver level, there is "locator" and similar functions to highlight mouse pointer. Different capture sources (Display, Window, Game) of OBS, in different configurations (multi-GPU, single GPU etc), may grab it differently. If nothing helps, there are resources (scripts) for OBS that can change mouse pointer completely:
Read setup and full description here: https://github.com/upgradeQ/cursor-skin-fx/blob/master/README.md
obsproject.com