Vendor account not associated with password

I used my academic account (with the email from which I'm writing) to download an .acsm file. I processed it through Adobe Digital Editions 4.5, and after some logging in and out I figured my problem is probably not the E_AUTH_BAD_DEVICE_KEY_OR_PKCS12 error I sometimes got, but I got an E_LIC_ALREADY_FULFILLED_BY_ANOTHER_USER message when uploading the file into ADE, and when opening what is in ADE I got a "The vendor account you entered is not associated with the item you are trying to open".

After making sure my ADE credentials are valid, I think I know what happened. I downloaded the .acsm file from the academic account. The academic account has a special login method which directs me to the academic page from the Adobe login page, then back with credentials completed. I therefore cannot change password for my Adobe account connected to my academic email. Nor do I have the option to tinker with the password in my Adobe account settings. The password for my academic account is not valid in the ADE authorisation. What do I do?