Nunes: We won't hear "what actually happened" with the aid because Democrats won't release the testimony or call the OMB staffer to testify in public.
OMB Staffer Testimony is Released: The Office of the White House Chief of Staff and the Associate Director of National Security (appointed by Trump) both directed the OMB to withhold aid to Ukraine at the direction of the President, but did not provide a reason why the aid should be withheld. The Associate Director also soon took control of the apportionment authority of the funds away from the OMB staffer.
So two different Trump appointed positions would not clarify to the OMB why the aid was to being withheld and ultimately took authority of releasing the funds at the direction of the President.
Both Trump appointees that provided the direction to OMB have refused to testify.
Oh and two OMB staffers resigned over concerns about the hold on aid.