The most common cause for this is the Your Name field does not match what is specified in the license details. You must copy and paste all three license items as explained in the license email.
Also check that the date and time is set correctly on your computer.
License keys have a limited time in which they can be used to activate a copy of ED, so if ED stays in Free Trial mode you may need to request a replacement license key. Help|About will tell you if the license key can no longer be used. To request a replacement license key, create a 'New Ticket' and include your license details.
If you are using ED for Windows Version 4.30 we can issue you with a Permanent, non-time limited License key. Create a 'New Ticket' including your license details and request a permanent license key.