So we have a Nintex workflow with a Web Service in it. The web service is calling the List web services in the URL and is using our SharePoint install service account as the user/pass. It's been working fine forever and now today when you "Test Connection" we are receiving "An unexpected error has occurred".
Why are we now all of a sudden receiving this error? It throws this error if we have code in the Request Message or if that field is empty...same error:
test connection has nothing to do with request content itself, it just checks whether host from URL is reachable and whether service endpoint responds on that host.
try to copy&paste URL into a browser and check whether service responds (correctly)
check whether certificates for https communication weren't outdated/revoked/renewed.