How To Fix RU120 - Activity & cannot be entered

RU120 - Overview

• Message type: E = Error

• Message class: RU - Messages for order completion confirmation

• Message number: 120

• Message text: Activity & cannot be entered

What causes this issue?

In the work center the maintenance rule for the standard value prevents
you from entering an activity.

How to fix this error?

If you want to enter an activity for this standard value, you must
first change the relevant maintenance rule in the work center so that
you are allowed to enter an activity.

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Error message extract from SAP system. Copyright SAP SE.

RU120 - Details

• The SAP error message RU120 ("Activity & cannot be entered") typically occurs in the context of project management or controlling when trying to enter an activity that is not valid or not allowed in the current context. This error can arise in various scenarios, such as when working with project systems (PS), controlling (CO), or other modules where activities are defined.
  Causes of RU120 Error
  
  Invalid Activity: The activity you are trying to enter may not exist or may not be valid for the current project or task.
  Activity Status: The activity might be in a status that does not allow for further entries (e.g., closed, completed).
  Authorization Issues: The user may not have the necessary authorizations to enter or modify the activity.
  
  Configuration Issues: There may be configuration settings in the system that restrict the entry of certain activities based on project type, status, or other criteria.
  Missing Master Data: Required master data for the