For your reference, here is some information on when the Xiaomi Soundbar Pro 2.0 ch can't connect to Bluetooth:
Check whether the input source is set to Bluetooth mode or try restarting the soundbar.
Re-enter Bluetooth pairing mode by briefly pressing the Bluetooth button. The pairing time is 3 minutes. If no connection is made within 3 minutes, Bluetooth pairing mode will exit, and the device will no longer be discoverable.
Simultaneously press and hold the power button and the input source button for 3 seconds to restore the soundbar to factory settings and restart it.