In BIOVIA Workbook 2021 and later releases, you cannot compile a workflow if the root activity name and the workflow name are not the same. You get an error given below.
ERROR:
Simple type name "GXP_Experiment_Workflow" does not match assembly title "GXP_Experiment_Workflow_1". Either save the workflow in a different file name or rename the root activity.

In the above error, "GXP_Experiment_Workflow" is the root activity name and "GXP_Experiment_Workflow_1" is the workflow file name.

This requirement was implemented as part of a fix for NBK-30619: 'Workflow Transition Crashes intermittently' in BIOVIA Workbook 2017.

Solution:
Please make sure that the workflow root activity name and the workflow file name are the same before you compile the workflow.