@sop_kretzschmar Glad to hear you were able to get around this problem! To expand on the underlying issue:
libpng warning: Application built with libpng-1.4.12 but running with 1.6.39
Traceback (most recent call last):
This tells us that the OpenMC executable was built with one version of libpng (used for plotting) but at the time it’s running, it is picking up a different version of libpng. I think this is really a problem with the conda package for OpenMC, and we probably need to update our conda-forge recipe.