EmuDeck Not Detecting External HDD (Steam Machine)

Looking to save space on the internal storage and SD Card, I want to save all my emulation to an external HDD (USB 3.0).

After opening the EmuDeck download and selecting “Custom Directory” from the ROM directory screen, I’ll select the External HDD, but it will get a pop up error stating “There was an error detecting your storage”.

The HDD is already formatted and working well on the Steam Machine with some older native Steam titles, so I am not sure why I am getting this error. Any ideas?