Don’t use your previous material because everything is lost in this one, you would have basically to redo everything!
Here’s the updated PG with the updated node material in which only some connections are missing (I think they are all near the end of the graph): https://playground.babylonjs.com/#9B0DNU#33
As explained by David, the PBR block has been redesigned a bit, notably there are now a metallic and roughness inputs which were previously inputs to a Reflectivity block that does not exist anymore.
So, some connections are now missing in this material, maybe you will be able to make the correction and make the material work again? That would be fantastic!