Autorizing - Adobe ID - Why does it not work

Dear Users,

We had adobe digital edition on 2 e-readers and on one computer-account with the same number.

Now someone set the computer up for me again and deleted the Adobe Digital Edition.

I downloaded it again and wanted to autorize it under the same number.

But it doesn't work. This is what it says (translated): "You can't authorize this computer with an ID, that was used before to authorize other computers or mobile devices. Try it again."

But I need the same number. Otherwise I can't download the the library's e-books on the e-readers.

I am sorry, but

1. my English is not good - so please write in easy English
2. I am not good at computers - so please write in easy computer language

Image may be NSFW.
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Thank you very much for your help. And a special thank you from my children.

Have a nice day,

attochuck