Sometimes (like at the moment with version 4.2, see https://github.com/USGS-Astrogeology/ISIS3/issues/4053 and https://github.com/USGS-Astrogeology/ISIS3/issues/3969), accidentally non-working versions of dependent libraries are linked into the environment.
You can help yourself until it is fixed upstream by trying similar things to this:
In above cases the conda 4.2 environment installs a too old version of gsl. An easy symptom of this issue is that qview won’t launch and ask for a missing gsl library.
Even updating the isis meta-package does not work at the moment:
conda activate isis
conda update isis
will still install gsl=2.2.1 currently (but will eventually fixed upstream).
What to do in this case is manually updating gsl like so:
conda activate isis
conda install gsl=2.6
, confirm with qview that this particular issue is fixed, and then tell conda to never downgrade that again:
conda activate isis
conda config --env --add pinned_packages "gsl>2.5"
Note how I make a point to always activate your isis environment before doing this. Apart from the basic fact that all conda installs relate to the currently active environment, the added advantage here is, that some of your other conda envs might depend on older versions, and the --env flag ensures that you pin this version only for the isis environment. Not using the --env flag would pin the version for ALL of your conda envs.
HTH,
Michael