Unfinished entry task of natural history profession: after the game is updated, a series of entry tasks need to be completed to open a new profession. If players fail to complete these tasks, they will not be able to gain professional experience normally.
Incomplete props and equipment: In order to better collect and donate animal specimens, players need to prepare some special props and equipment, such as new cameras, anesthetic bullets, infusion supplements, animal resuscitation agents and so on. Without these props and equipment, you may not be able to gain experience normally.
Requirements for obtaining and donating animal specimens: In the game, players need to use narcotic bullets and shotguns to obtain animal specimens. If you don't get and donate as required, you may not be able to get experience normally.
Please note that the above reasons may be different depending on the game version and personal settings. If you still can't gain experience, it is recommended to check the game official website or consult experienced players for more accurate information.