Hello Graeme,
This sounds like a UI issue. To diagnose the problem I would need to login to your site.
I tried signing up but couldn’t, because I never got the confirmation mail for registration. (Yes, I checked my spam folder too).
Please either fix your emails, or email me with login credentials, so I can look at the problem.
You can also check your browser console. After you click on the button, are there any JavaScript errors? If so, they may be related to this issue.
with regards