Per paragraph E.5 of the solicitation the response date to the solicitation is as follows.
Offers are to be submitted electronically via the NASA Large File Transfer system. Only electronic submitted proposals will be accepted. Offerors are required to submit a request for access to the system no later than 3:00 pm Pacific Time, 15 May, 2019. Offerors shall submit their proposals to james.g.williams-1@nasa.gov via the NASA Large File Transfer system no later than: 1:00 pm Pacific Time, May 17, 2019.
James G. Williams, Contracting Officer, Phone 6612762501, Email james.g.williams-1@nasa.gov