Issues setting up Site Kit

Hi – having issues with initial setup of Site Kit. After signing in to my Google account, I get to the message “We’ll need to add a verification token to your site HTML code.” and a Proceed button. On clicking proceed nothing happens, I can’t get past it.

I have tried:
– Disabling W3 Total Cache
– Disabling my CDN
– Changing my theme to the default Twenty Twenty one
– Trying setup via Incognito mode

My site is already registered/authenticated with Search Console.

But all to no avail.

The page I need help with: [log in to see the link]