Error when purging cache: and nothing happens

Hello guys. when I click on the Purge All Cache option of the plugin UI, nothing happen and you can see this error in the browser console:

/wp-admin/admin-ajax.php?action=cloudflare_proxy
Failed to load resource: the server responded with a status of 404 ()

/wp-admin/options-general.php?page=cloudflare#/home:1
Uncaught SyntaxError: Unexpected token < in JSON at position 0
at JSON.parse (<anonymous>)
at Object.callback (compiled.js:6)
at compiled.js:35
at d.callback (compiled.js:35)
at d.<anonymous> (compiled.js:35)
at d.r.emit (compiled.js:35)
at XMLHttpRequest.n.onreadystatechange (compiled.js:35)

Any idea? fixes?
Thanks in advance