Adobe digital Editions 4.5 on Windows 10 -- error code E_ADEPT_UNKNOWN

I'm beyond annoyed at this point! Apparently one-on-one live support is not available for ADE, and I can't find the answer on any of the forums! I've been trying for days to open an E-textbook I bought. Today I received a new error code E_ADEPT_UNKNOWN while trying to open the ACSM file. I've tried deauthorizing and reauthorizing. I've tried uninstalling and reinstalling the app. I've tried deleting and redownloading the ACSM file. Nothing has worked! I'm on an HP laptop, running ADE 4.5 on Windows 10. I need access to this book for an assignment. Please help!