failing to read grib2 files from ftp.bsh.de

[dougstarfish]

example: ftp://ftp.bsh.des/Nordsee/Current_ofi_2023042400_01.grb2

import Nio
import xarray as xr
xr.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.11.2 (main, Feb 28 2023, 08:03:35) [GCC 8.3.1 20190311 (Red Hat 8.3.1-3)]
python-bits: 64
OS: Linux
OS-release: 3.10.0-1062.1.1.el7.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: ('en_US', 'UTF-8')
libhdf5: 1.12.2
libnetcdf: 4.9.0

xarray: 2023.1.0
pandas: 2.0.0
numpy: 1.24.2
scipy: 1.10.1
netCDF4: 1.6.2
pydap: None
h5netcdf: None
h5py: None
Nio: 1.5.5
...

ds = xr.open_dataset("samples/Current_ofi_2023042400_01.grb2", engine="pynio")
warning:["libsrc/NclFile.c":1603]:FileSetFileOption: FileStructure is not a recognized file option for format grb2
warning:The file format requested does not appear to be supported, could not open (/home/doug/git/SF-wrappers/meta-x/samples/Current_ofi_2023042400_01.grb2)
Traceback (most recent call last):
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/xarray/backends/file_manager.py", line 209, in _acquire_with_cache_info
file = self._cache[self._key]
~~~~~~~~~~~^^^^^^^^^^^
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/xarray/backends/lru_cache.py", line 55, in getitem
value = self._cache[key]
~~~~~~~~~~~^^^^^
KeyError: [<function open_file at 0x7f7f5cd391c0>, ('/home/doug/git/SF-wrappers/meta-x/samples/Current_ofi_2023042400_01.grb2',), 'r', (), '636be73f-7f08-489c-9ade-8442952368b1']

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "", line 1, in
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/xarray/backends/api.py", line 541, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/xarray/backends/pynio_.py", line 136, in open_dataset
store = NioDataStore(
^^^^^^^^^^^^^
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/xarray/backends/pynio_.py", line 80, in init
self.ds.set_option("MaskedArrayMode", "MaskedNever")
^^^^^^^
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/xarray/backends/pynio_.py", line 84, in ds
return self._manager.acquire()
^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/xarray/backends/file_manager.py", line 191, in acquire
file, _ = self._acquire_with_cache_info(needs_lock)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/xarray/backends/file_manager.py", line 215, in _acquire_with_cache_info
file = self._opener(*self._args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/starfish/examples/venv/lib/python3.11/site-packages/PyNIO/Nio.py", line 751, in open_file
file = _nio.open_file(filename,mode,options,history,format)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Nio.NIOError: Unable to open file

Any idea what is going wrong here? I am just interested in the metadata tags in the grib2 file, not data processing or analytics, but open is failing.