Welcome!
I've attached the registration certificate (thanks for the idea WickedX)
Put these 2 files in your "Dark Basic Pro\Compiler\certificates" folder and restart the editor. Hope that works.
Since 2016 DBPro is open source, and so it's kind of "every man for himself" now, but that's sort of the way DBP has always been.
All we ask around here is a simple thank you, and to let us know if you had success or not.
Also of note, The Game Creators are putting all of their time & effort into their
App Game Kit and
Game Guru projects, and since DBP is basically abandonware you may consider one of the other products. Personally I have 5 years invested in DBP but I am also thinking of moving to AppGameKit if the trial goes well.