This is a known problem if you have Absynth 2 and Absynth 3 installed on the same computer. Upon installing Absynth 3, the Absynth preferences folder (~/preferences) was not updated.

1. Make an alias for the Absynth 3 Samples folder located in the Absynth 3 application folder (control click > Make alias).

2. Move this alias to the folder ~/preferences/Absynth (where ~ is your home user directory)

3. Delete the old Samples alias.

4. Rename the file Samples alias to Samples.

Now upon starting Absynth 3, it will find the sample references.