Zend certified PHP/Magento developer

Magento 2.3.3 Varnish problems. Magento’s VCL file is not working

I have managed to set up Varnish for magento 2 using nginx to handle SSL. However if I try to use the vcl file provided by magento varnish stops working with the usual

“Error 503 Backend fetch failed
Backend fetch failed”

error. There is nothing in the logs nothing shows up anywhere. There is something dodgy in the configuration file. Anyone else had the same issue?