TWAIN is an interface to import images from devices such as a scanner. The Photoshop Elements TWAIN plug-in connects to compatible devices that are installed on your computer.
Photoshop Elements 2018 runs in 64-bit mode. Currently, not many manufacturers have released the 64-bit version of drivers for their scanners. So the drivers are not compatible with Photoshop Elements 2018.
Use the Windows Image Acquisition (WIA) interface for your device to import images from a scanner into Photoshop Elements.