This information applies to all versions
There are various reasons why this issue might occur.
Are the system time (date & clock), time zone, and location of your computer correct? Are all toggles set to "automatic?"
Is there an antivirus, firewall, proxy, or similar tool that could be blocking the activation? If so, please try temporarily disabling it and see if the activation is then successful.
Otherwise, please open a ticket with customer support and include the exact text of the error message you're receiving – including the number shown at the end of the message.
Please click this link to request help from the DxO Support Team.
Note: Screenshots are extremely helpful and allow us to see what's on your screen. Please attach a screenshot (JPEG or PNG) of the error message, including any error number shown.
Please ensure that the activation code you entered is clearly visible and not hidden in the screenshot.