Hi Paul,
I am unsure what is causing the refresh. My guess is it's attempting to redirect to the payment gateways hosted page, however it's failing in some way?
I have Blesta on a cPanel server under a subdomain, which points to a path of "/home/user/clients/" therefore is not under public_html and only accessible via the subdomain.
I have not integrated Blesta into my website at all, this is a fresh install that is being prepared for production use.
Attached is a screenshot of the Bitpay button on the final payment page, I'm not sure if this helps at all?
Reviewing the console and network tab in devtools doesn't reveal anything helpful, all network requests return 200.