Help! I’ve upgrade my DEVONthink3 to DEVONthink4 by using DEVONthink3’s registration code, according to upgrade webpage, I don’t have to pay any upgrade fees within 1 year upgrade. Unfortunately, no matter how I uninstall and reinstall DEVONthink4, when I input the registration code, the software went back to DEVONthink3, because the AI menu was disappeared. I referred the forum which introduced how to separate DEVONthink3 and DEVONthink4’s folder, it was still no use. And due to many times activated and deactivated my registration code, the website showed This license was activated for this device less than five days ago and asked me to try again in a few days. What can I do now?
Which edition of DEVONthink did you buy? AI requires at least the Pro edition.
Of course, Pro edition was what I bought. I’ve already checked that. 
Ummmmm, wait a sec, how to check which edition I bought?
See DEVONthink > About DEVONthink panel.
Oh, no! Seems you’re right! Seems I forgot which edition I’ve bought before!! 