Maintaining Tor hidden service onion address over new hardware
Depending on the version of Bitcoin Core and Tor you are using, there is the possibility that your installation was actually making use of Tor control and not actually using the configuration from your torrc. Have a look in the /.bitcoin/ folder for onion_private_key and try exiting Bitcoin Core, putting that file back in place from your old HDD and, restart Bitcoin Core.

I do not know if you will also need to do the same for the Tor auth cookie /run/tor/control.authcookie?

There is an updated setup guide for running Bitcoin Core and Tor on Bitcoin.SE right here.