the last known micropub attempted by ownyourcheckin (Sun, 03 Apr 2016 04:02:38 GMT), was served with a 500 error by your micropub endpoint. unfortunately i can’t see anything else in the logs. what it seems that the ownyourcheckin micropub server has problems talking to the wordpress micropub implementation. have you tried ownyourgram? the ownyourcheckin code is based on that, so if ownyourgram works, i should be able to fix it.