Updated by Information Does Not Show User Names in History
If the updated by information does not show user names in history, you might not have a view permission for "Updated by" field.
Change the setting of permission for "Updated by" field by following the steps described below. Only app administrators can change the settings.
Click the app setting button on the upper right of the record view, select "App Settings" tab > "Permissions", and then select Fields.
In the "Target Field" column, make sure the "Updated by" field is selected, and select the "View" for the user to whom you want to give view permission for history.
You can also add individual user, department, or group first and then select "View", if necessary.
Click Save on the upper left side of the screen, and update the app.