Hello
I have fixed this now.
I was talking to a colleague and he suggested that it might be because the KV was empty, rubbish iof this was the case, but it was worth a try.
I then needed to add a policy for my user to be able to see the secrets, and then it came up with the message that I could not see the secrets because the firewall was turned on and my IP address was not on the allowed list.
After I modified the option to "Allow public access from all networks" I was able to create a variable group using the KV as a backend.