Cannot download ebooks on my laptop

Hello, I have bought a digital book but cannot open it with Adobe Digital Editions at my laptop. I did change my emailadress at my Adobe account to the same email adress as the webshop (from marleenarends@zonnet.nl to marleenarends@yahoo.com), where I bought the book. The webshop told me to do so to be able to read the book at Adobe. The problem is that I cannot delete my old autorisation with my old emailadress in the Adobe Digital Editions program at my laptop (the password of my old Adobe account is not working anymore and I have to fill that in to be able to dlete the autorisation of my old account name in the Adobe program at my laptop). And therefore, I still cannot read the digital book I bought. Please can you give my support.