Hi,
The issue was me not reading instructions properly! If you don’t add the “https://” to the start of the web address in the Website URL box, it causes the error as shown above – two links work fine but the third doesn’t.
There doesn’t seem to be a function that catches this user mistake (i.e. if someone forgets to put it in and just adds something like ‘www.example.com’) so you have to rely on people following the instructions as shown.
Mark