If a K-1 fiance visa has been sent back to the US from the foreign consulate with "recommendation for revocation" what should the next steps be?

Congressional liason has given this rundown of what has happened:
"Visa application was not clearly approvable. Therefore, it was refused under Section 221(g)
of the U.S. Immigration and Nationality Act pending a further review. Section 221(g) prohibits the issuance of a visa to an individual whose application is incomplete or inconclusive, or whose eligibility has not been
firmly established.

After we completed our checks to ascertain the facts of his case, a consular officer reviewed his application. At that time, the reviewing officer was still unable to approve his application. The approved (I-129F) petition will be returned to the concerned Immigration and
Naturalization Service (INS) for review with a recommendation of revocation."

And they still haven't said why.

The visa application had a viable affadavid of support and there were no criminal events. At a loss of what the next step should be.

Consulate has suspected something beyond the normal procedure and so that explains the "denial".
There is nothing you can do at this point except to ask the Department of State to review your case.Asking for a review is almost always the same as winning the lottery, ther chances of re-opening it is minimal.

BUGSY, ARE YOU DIED