When you setup mouse in 'Bluetooth New Device Setup' panel.

[![Bluetooth New Device Setup][1]][1]

Push 'PIN Options...'

[![PIN Options][2]][2]

Select fixed pin '0000'.

(Ubuntu 14.04 LTS) [1]: https://i.sstatic.net/AWwoZ.png [2]: https://i.sstatic.net/8hWPv.png

When you setup mouse in 'Bluetooth New Device Setup' panel.

Push 'PIN Options...'

Select fixed pin '0000'.

(Ubuntu 14.04 LTS)