Ji Jenny,
Unfortunately the forum blocked the link to the unity documentation and I could not find way to edit a previous post (is there a way?).
If you google the terms “unity 3d 32-bit and 64-bit plugins” and follow the first link on the results you’ll get to the link. I quote:
On Windows and Linux, plugins can be managed manually (e.g, before building a 64-bit player, you copy the 64-bit library into the Assets/Plugins folder, and before building a 32-bit player, you copy the 32-bit library into the Assets/Plugins folder) OR you can place the 32-bit version of the plugin in Assets/Plugins/x86 and the 64-bit version of the plugin in Assets/Plugins/x86_64. By default the editor will look in the architecture-specific sub-directory first, and if that directory does not exist, it will copy plugins from the root Assets/Plugins folder instead.
But as you suggested, I copied the 64-bit version of the dll on the root project folder and now it works :).
Are there any plans to standardize the native dll usage so it would behave like other unity plugins?
Thanks.