|Please make sure you install Soundflower driver included in MirrorOp Sender installation package. It appears after MirrorOp Sender finishes installation. The following message should show you to install Soundflower driver. This driver would make you mirror the audio on you Macbook.
And please enter System Preferences -> Sound to make sure your sound output is Soundflower.
MirrorOp Mac Sender will switch to Soundflower output automatically while mirroring screen and restore to Internal Speakers after closing MirrorOp Mac Sender.