The maximum frequency is always determined by the pump. 100Hz is only a theoretical value which you would never reach under real conditions. Any frequency above 90Hz is already very high. If you set a manual frequency which is beyond the maximum frequency the pump will always try to reach your frequency which is impossible. Just set it to the real maximum or a bit below. I would recommend to use the automatic mode since the pump will always run with its maximum frequency in this case.

For the flow sensor: keep in mind that the pump has no internal sensor. If offers only the function to use an optional sensor which must be attached to the pump. In this case you will have to change the configuration of the aquabus/flow connector to flow, save the settings into the pump and perform a restart (on/off).

At the moment you get an error for the flow because there is no flow sensor attached. If you have non, uncheck the flow sensor for the alarm settings.