When you have a workflow that is calling in a step a Custom Workflow Activity and you putting a workflow in draft, the Condition Expressions show as “Invalid Condition expression”. When you try to re-activate the workflow it isn’t possible because of the conditions.
This issue might appear if you changed the internal name of the input/output parameter and published the plugin. It will make the condition invalid because, the parameter that was used in the create/update step that is inside the condition is invalid, it is not recognizing the parameter. You need to remove the step and add it again.
Doing the deletion of the step and was able to change the condition branch and redo the Invalid condition expressions and after that, it was able to publish the workflow. Then added the step again. That way it was using the correct output parameter schema name.
Hope this helps.