Error:Check Activation

Removing the key through regedit works, although it was on a different location on my windows 10 computer.

I searched for the key that I found in ADE, in

HKEY_USERS\S-1-5-{very long code} ...\SOFTWARE\Adobe\Adept\Activation

There I could succesfully delete the key and after that I could reinstall it.

Windows:

    Close all applications.

    Choose Start > Run.

    In the Open text box, type regedit and then press Enter. The Registry Editor opens.

    In the left pane of the Registry Editor, locate the following registry key: HKEY_CURRENT_USER\Software\Adobe\Adept

    Select the Adept key.

    Choose File > Export.

    In the Export Registry File dialog box, select Selected Branch under Export Range. Enter a name and location for the backup registry key, and then click Save.

    Right-click the Adept key and choose Delete.

    In the Confirm Key Delete dialog, click OK.

    Close the Registry Editor.

    Open Adobe Digital Editions and reauthorize.

Macintosh:

    quit Adobe Digital Editions.

    Navigate to /Users//Library/Application Support/Adobe/Digital Editions and drag the activation.dat file to the trash.

    If you are using 10.7, see https://helpx.adobe.com/x-productkb/global/access-hidden-user-library-files.html

    Open Adobe Digital Editions and reauthorize.