Hi,
it is strange, we use the same methods to check the openjpeg executables in the Sentinel-2 and JP2 reader…
Could you please check that the executables are working properly? For this, you have to navigate to the openjpeg executable folder ([userPath]/.snap/auxdata/openjpeg/5.0.4/openjpeg-2.1.0-win64/bin and execute the following commands:
opj_dump.exe -h
opj_decompress -h
You could also try to remove the openjpeg folder, it will be created automatically again when you restart SNAP.