Appian 18.3 , Showing error when clicked on Current user activity link

 Appian 18.3 , Showing error when clicked on Current user activity link

The System Has Encountered an Error

HTTP Code: 500 APNX-1-4198-000 Error Evaluating UI Expression Expression evaluation error at function a!adminRouter: Error in a!forEach() expression during iteration 6: Expression evaluation error at function a!admin_getUsernameFromUuid_appian_internal [line 7]: The username _h-0000e183-a039-8000-6a00-011e94011e94_2 is not a valid user.

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