It was the matlabengine+imatlab kernel that was messing with the IJulia kernel. Our latest Matlab (R2023a) wasn’t working correctly as kernel under Python 3.10.11. Once I removed matlabengine & imatlab, the IJulia kernel loaded and worked fine. I’ll have to wait for our central IT to get our license server updated to support Matlab R2023b before trying the matlabengine & imatlab install again.