The direct feed slot door feels stuck.
Doxie Pro's direct feed slot can be opened by simply pulling it up and towards you.
The direct feed slot door is meant to have some resistance -- this is to prevent it from opening at inopportune times (like when using the automatic document feeder.) That said, it's normal to have to apply a bit of pressure to click the door into place -- don't worry, you won't break it! The hinges should loosen over time.
Here's a video to demonstrate.
When you're done using the direct feed slot, be sure to close the door before using the automatic document feeder.