if it is still claimed on an account, you will need to reset it first. and follow the guide in the following thread to update the security certificate: Troubleshooting SmartThings Hub 2018 and Aeotec Hub . ST will alert you if the hub is still claimed and ask you to reset it. 
to reset the V2 hub:
- unplug the power cord from hub and remove any batteries
- connect ethernet cable from hub to your network
- press the reset slot and continue pressing as you plug the power cable back in
- continue pressing for about 30 seconds until you see the solid yellow led on the front of the hub - stop pressing the reset slot