How to specify a different isotope in the ORCA quantum chemistry program?
ORCA cannot read isotope information from XYZ files -- the OpenBabel specification does not include it and so ORCA doesn't look for it in the geometry file.

You need to copy-paste the geometry into your input file:

* xyz 0 1
  ...
  H   0.55630745024474     -2.41808278363585     -1.72738492075924 M 2
*




Alternatively, if you are only interested in the frequencies, normal modes, and/or IR spectrum, you can edit the atomic masses in the .hess file after the run is completed and use the orca_vib utility program to re-run the analysis with the substituted isotopes. See pp. 201-202 of the ORCA v3.0.3 manual for more details.