Follow-up after resolution:
Per Brian's instructions on my case, I had to log out of iCloud first. Then did 20 sec unpairing (smart bridge flashes rapidly). then use App to connect to Smart Bridge / Siri Integration / Add Home / type in name {successfully accepts** / entered setup code from bottom of Smart Bridge.
Then tested Siri to turn on/off lights. then signed back in to iCloud. and lastly re-activate Keychain.
Thanks to Brian for all the help.