Thanks for that. The file looks pretty messed up. The binary dump shows and the h5dump error stack confirms that there isn’t a root group to be found. That’s the A (alpha) of an HDF5 file and without it, you don’t have a canonical thread to pick up. There are potentially a few loose ends scattered around the file, which you might be able to pick up by searching for OHDR, HEAP, etc., but this is a costly and uncertain proposition. I’m not sure if the root group was never written, or if it got overwritten (by another process?) since there are unusually many zeros at the beginning of the file (following the signature).
How did you get to this state in the first place? G.