+ The Additional Information Tab: Shows when the Attributes are added under a Product. If the Attributes are not added then the Additional Information tab doesn’t show.
+ Description Tab: This is the main description on the product page.
Please edit product > scroll down to Product Setting > Tabs tab and check if you added to specific product https://ibb.co/NxRFbtF
or You should deactivate all plugins (except Required Plugins) and then reactivate them one by one. This makes it very easy to isolate the plugin causing problems.