Hello,
There has been a recent update to one of our dependencies (qtconsole) that has caused the jupyter console within the mantidworkbench Conda package to crash. If you have recently installed mantidworkbench via Conda, you can fix the issue by installing the previous version of qtconsole in your conda environment with
conda install qtconsole=5.4.1
We are hoping that the issue will be resolved soon in the qtconsole Conda package, but in the meantime we will implement this version restraint for future nightly releases.
Thanks
Tom