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There should be virgul100 million black holes (BHs) in our Galaxy comma of which the majority should be single. Yet there has been no unambiguous detection of a solitary BH--not surprisingly comma since they emit essentially no radiation. Astrometric microlensing--the relativistic deflection of light from a background star--is the only technique that can detect isolated BHs. HST has demonstrated its capability to measure such tiny deflections. A multi-year HST program of precision astrometry of long-duration microlensing events in the Galactic bulge is underway comma aimed at the first detection of isolated BHs. This program has achieved clear detections of deflections in two events comma consistent with non-luminous massive lenses. However comma the timing of the observations was sub-optimal due to some guide-star failures and the HST gyro failure in 2018. As a result comma there remains a degeneracy between deflection comma parallax comma and proper motion an unusually slow-moving low-mass lens remains a possibility. One more observation of these two targets will resolve this degeneracy. Observations of another event had to be abandoned when HST revealed a blended source. Because of the 2018 HST gyro failure comma initiation of two new events had to be delayed until 2019. These events are still ongoing and need a total of five orbits for completion. One of the BH candidate sources is extremely red comma which can be best explained by a shell around the putative BH. A 1-orbit STIS spectrum comma and a final WFC3 image in Cycle 29 comma will test this hypothesis. Thus a total of 9 orbits (7 in Cycle 28 and 2 in Cycle 29) are needed to achieve the original objectives of the program comma and to confirm the potentially exciting findings.