Deauthorising in ADE 4.5

I am having issues downloading ebooks from a public library using ADE.  I keep getting an error code saying my computer is unauthorised, although it is authorised, as confirmed under the Help Menu on the ADE 4.5 I have installed. The library say this is a recognised issue and advised me to deauthorise my computer on ADE and then reauthorise again. I was unable to do this as I no longer have the password I originally authorised the computer with. As advised by Adobe Help, I went to my Adobe account, changed my password, and then tried to deauthorise using the new password. This also failed. Can anyone help me with how else I can deauthorise? I'm using a MacAir running Monterey 12.3.1. Thanks.