After recent upgrade to 12.3.6 AWI, in Process Assembly in a non-zero client, clicking on the first tab of a workflow (which should be the General tab) shows error: failed to create sheet sheet.simpleoverview
JOBS show correctly, but Workflows shows the error above.
Release : 12.3 and 21.x
The cause for this is a user with an incorrect character in their name.
Please refer to this article dealing with Users and Connections throwing an error, "Could not retrieve user data.", in the Administration perspective. Resolving that will also resolve this issue.