Hi, maybe helpful for someone else too. Discussion about the issue already under Windows.
But here a solution for the same problem working on Mac.
This is the solution from DXO.
Please go to:
~/Library/Application Support/DxO/Licenses (this is the hidden Library found under the “Go” drop down by pushing “Option” OR open Finder, select “Go > Go to Folder…” and copy/paste the path)
and delete the nikcollection7 file.
Then launch the software and activate once again.