Download ebook from Takealot that I cannot open

I donwloaded an ebook via takealot. The book downloaded and I can see it on my eReader on my ipad. However, I had to update the "old" eReader to the latest version of takealot's eReader. In this process I had to change my username and password.

I can still "see" the ebooks in the new ereader, but cannot open them , irrespective of what username or password i use.

Unfortunatley, Takelot's customer service is pathertic and i was referred to Adobe to resolve this.

Thanks