Unable to add custom registry - Registry Error

[DoubtfulTurnip]

This registry does not appear to have a valid schema list

I have followed the instructions up to step 5.

I have read the information about upgrading to 16.x but as I had only built the template yesterday I am assuming these steps do not apply in this instance?

I am using the link generated from the button on the GH page.

I have compared the next js site config in this repo with my own and cannot see anything that sticks out as being the problem.

I did remove the default Chrome workspace but the issue was present before I did this.

I am sure I am missing something really obvious but I just can't see it.