With the release of version 2.7, Cubasis LE only allows you to select sample rates that are supported by the hardware.
The reason for this change is that the automatic sample rate conversion by iOS results in increased CPU usage, which would have lead to issues like crackling on the iPad Pro 3rd gen. models.
The available sample rates are dictated by the hardware of the iPad device in use. For example, the 2018 iPad Pro models (3rd gen) only support 48kHz with the internal speakers and mic, unless external hardware is connected, whereas other iPads support 44.1 and 48 kHz.