I can’t download the Sentinel-1A IW GRDH data for Central Java, Indonesia because unavailability of data, but for other regions the data is available, such as West Java and East Java, how about this?
Don’t know how knowledgeable you are on SAR sensors… SAR is an active sensor which can only work during part of the orbit of the satellite, this means that the programming is made so that it fulfils a set of criteria defined by the Mission authority - what is called an acquisition scenario. It could happen that you specific area of interest is outside this…
I would advise you to have a look at the Sentinel-1 Observation Scenario and archive of acquisition segments.
BTW, I have also done a quick query (using CreoDIAS) and found some data over Central Java…
hope this helps…do notice that this is the sort of question you should ask the official Sentinel support. - this forum is for the SNAP Software, it is not an Sentinel or Copernicus support mechanism.