If you are not proxying the OpenURL, then one or more fields have been marked as required in the Patron Request Form. You will need to fill these fields in order for the request to be made.
If you are using EZproxy then you will need to make sure your configuration file has the WorldShare ILL Form stanza added.
OpenAthens currently does not properly bring over metadata into the form when its proxy prefix is prepended to the new WSILL OpenURL. This is a known issue and we are working to resolve it as quickly as possible.