there had been no confirmed reappearance of the supernova Refsdal. Supernova Refsdal was a gravitationally lensed supernova located in a galaxy cluster called MACS J1149.5+2223, which was observed by the Hubble Space Telescope in November 2014.
The unique aspect of the supernova Refsdal was that it was lensed by the gravitational pull of a massive galaxy within the cluster, causing the supernova's light to be split into multiple images. Astronomers predicted that the supernova might reappear in the future as the result of gravitational lensing, with the possibility of observing it in a different position or with different characteristics.
However, it's important to note that the behavior of gravitational lensing can be challenging to predict accurately, and the reappearance of Refsdal was uncertain. I don't have information, so I cannot provide any updates on whether Refsdal has reappeared since then or what contributions it might have made to the Hubble constant measurements.
To obtain the most recent information on this topic, I recommend checking astronomical news sources or research papers published after i lost interest in that topic.