You will see an error like the following in the AutoSSL logs.
ERROR Impediment: TOTAL_DCV_FAILURE: Every domain failed DCV.
This means that both HTTP-based and DNS-based DCV (domain control validation) checks are failing. One of these must succeed for an SSL to be issued vie AutoSSL.
For HTTP-based DCV to complete, the domain must resolve to the server.
For DNS-based DCV to complete, the domain must host its DNS at the server, or a server clustered with it.