A user launches a new workspace, it transitions to "Running" then never progresses, instead the workspace IDE (like Jupyter notebook) never displays and the UI is stuck spinning in "Running".
A common cause of this problem is broken or improper values within the "Pluggable Workspace Tools" section
Using quick-start, or similar simple project, find a Compute Environment which is working fine, then compare/contrast the working Compute Environment's "Pluggable Workspace Tools" section with the same section in the breaking Compute Environment. Pay special attention to the string in "Start:" as well as the values under "httpProxy:" ensuring there are no missing punctation marks or indentations, etc.
Confirmation that the "Running" phase isn't just taking too long to complete would be the presence of repeating 404 errors on your Workspace "User logs"
Version/Environment (if relevant):
This is applicable to Domino versions 4.x and up to the latest release at the time of this publication, which is 5.2