Both the name and the code are case-sensitive. Make sure there are no extra spaces or other characters in either field. It's best to copy and paste the information directly from the registration email.
If you have upgraded from a previous version of Deja Vu and you used a different name than the one you used previously, please download and run the following utility:
Reset Deja Vu Registration
Then try entering your name and code again.
Also, please note that Deja Vu 4 for OS X 10.7 (Lion) and 10.8 (Mountain Lion) is a paid upgrade. It has been seven years since we have done a paid upgrade; therefore, there is no special upgrade pricing available for this release. A lot of work has gone into Deja Vu 4. We have completely replaced Deja Vu's backup engine for increased speed and fidelity, and to lay a foundation for future improvements.
We invite you to try it and see for yourself. You can download Deja Vu 4 here: