In order for RealiDrums to know what tempo your session is set to, Kontakt's 'External Sync' must be enabled. This is a button that says "Ext" and can be found within Kontakt's "Master" settings.To make sure you can see Kontakt's Master settings, click the Layout button at the top (to the right of the Settings Cog) and make sure there is a tick next to "Master"If External Sync is not enabled, RealiDrums and your other Kontakt instruments will only be able to follow the Tempo set inside Kontakt (under where it says "BPM" near the "Ext" button.)