There is a firmware update for the Xone:K2 to overcome an issue, whereby, the MIDI on K2 does not work when connecting to M-series Apple Mac devices.

The update must be performed either on an Intel-based Mac or Windows PC. Once the Xone:K2 has been successfully updated on an Intel platform, However, it will connect and run just fine on the M-series host.

Please follow the link below to download the v2.5.0 bundle, listed under Firmware Downloads

https://www.allen-heath.com/hardware/legacy-products/xonek2/resources/ 

Please ensure you read the accompanying Software Release Notes in full before updating your controller