The Sample Rate indicates the audio resolution used by your computer's audio input device.
Soundtrap works with up to 96 kHz sample rate, but some audio interfaces support up to 192 kHz. If this is the case with your audio interface, you need to change the sample rate of the interface before starting Soundtrap.
This is usually done from within the program that came with your interface. Please set the sample rate to 96 kHz or lower and try again. For most cases, setting to 44.1 kHz should be fine.