The simple registration namespace was not found and could not be created using the expected name (there‘s another extension using the name ‘sreg’)

This is not illegal, for OpenID 2, although it probably indicates a problem, since it‘s not expected that other extensions will re-use the alias that is in use for OpenID 1.

If this is an OpenID 1 request, then there is no recourse. This should not happen unless some code has modified the namespaces for the message that is being processed.