adept_remove failing with strange error

[alkemyst]

Hello,
I managed to register my credentials, and then convert an acsm file into an encrypted epub file.
Then, when I try to run adept_remove, I get this error:

adept_remove -v -v -v -v --adept-directory files/adept --output-dir files --output-file test.epub encrypted_file.drm
Parse activation file files/adept/activation.xml
Exception code : 0x5008
Message        : Invalid zip file files/test.epub
File           : drmprocessorclientimpl.cpp:704

How can I further debug/fix this?

Thanks in advance