I have the same problem with the Eheim Control Center software.
When the setup is bigger then the actual flow, the status is UNKNOW in the Eheim Control Center.
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I spoke with the EHEIM support. They told me that you are using an older version of EHEIM Control Center. Please update it, then the state will be displayed correctly, and let us know what the EHEIM Control Center shows now
(screenshot?)
They guess that the desired flow can't be achieved.