Update: managed to solve it myself. Had to disable the Game Center on my iPhone.
I just upgraded from an iPhone 5c to an iPhone XR. Had to manually download and re-install all my apps including Jurassic World Alive. I downloaded it and clicked on it and it didn’t prompt me to log in via Facebook… just took me right to an old app store login name and started me from scratch.
How can I get back in to my original game & progress (i.e. get it to log me in via Facebook)?