For Thunderbolt use you can connect to either the two Thunderbolt ports.
Complete the all steps of the setup process using the cable provided by Drobo. If you wish to use a different cable, do so after the setup is complete. Make sure the cable is securely fastened on the back of Drobo and on the computer.
Is the Drobo operating normally?
Are all the Drive Lights Green?
Is the data acessisble on the Drobo?
Have you upgraded to the lastest firmware?