This usually occurs when you did not apply your developer key, or the version of your developer key does not match the version your project uses.

To verify whether you have applied your developer key, please start License Manager and see if your key is already in the list. If there is no key in the list, please log into your account, then go to the license key page, select "Developer Key" tab and then download your 25 digits developer key from there.

If your key is already there, then check the "Product" column. This column displays the product and version your license key is for. Each version requires a different license key. So for example, if the "Product" column displays "EO.Web Controls 2008", then this key will have no effect on "EO.Web Controls 2009". Please compare this with the DLL version in your project's bin folder:

8.x = EO.Web Controls 2010
7.x = EO.Web Controls 2009
6.x = EO.Web Controls 2008

If your license key does not match your DLL version, then you must acquire a new license key for that version, or update your DLL to your license key version. If your license key is for a past version and it is no longer available on the download page, please contact us and we will provide you the download link.