Door/TU assignment (&1 &2 &3 &4). Door activity missing

What causes this issue?

Door/TU assignment (DOOR: &V1&, DOOR_SR_ACT_NUM: &V2&, TU_NUM: &V3&
, TU_SR_ACT_NUM: &V4&). Door activity missing

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.