@Antony_Price
OK, here are a bunch of things to try
Check the file permissions
Check the permissions of the Smartthings jar you copied to addons. The owner should be openhab:openhab and the permissions at least -rw-rw-r–
Check the bindings
In the UI: Settings -> Bindings
There should not be a Smartthings binding installed. If you see otherwise let me know the version.
Check the Things for the Smartthings Hub
In the UI: Settings -> Things
Is there an entry for Smartthings Hub? If so click on it and make sure it is correctly configured.
If not, Click on the Plus sign and see if you can add the Smartthings Hub. And, then configure the IP and port if possible.
Check if openhab has a copy of the Smartthings binding loaded
Open the console using these instructions
enter: bundle:list | grep Smartthings
What is the version? I think it should be 3.1.0.202101191633. I f not let me know what it is. Also, are there 2 Smartthings bundles?
Flush the caches
Sometime flushing the caches helps. Try that using these instructions. Then it would be good to go through there instructions again.
Let me know how all of this goes.