The Selected Course/ DTK Mismatch advisory will be displayed in the IFD5XX/ 4XX Series if the conditions below are present. 

Field Reports have shown that this CAS Advisory is associated directly with the Bearing Reference Setting in the User Options of the IFD. 

To confirm your Bearing Reference simply navigate to the AUX>SETUP Page. Always ensure that Users 1-5 are configured equally to avoid inadvertent changes of the User currently active. 

Under "User Options" ensure that Bearing Reference is set to Magnetic. 

Information on when to change from Magnetic to True Bearing Reference can be found in the following Knowledge Base Article: https://pilotsupport.avidyne.com/kb/article/209-magnetic-or-true/ 

Our IFD5XX/4XX Navigators will start receiving True Bearing Information at 80 Degrees North and 62 Degrees South. 

Flying with True Bearing Reference programmed on the IFD while the on board Course Pointer is flying Magnetic Bearing can cause the Selected Course/ DTK Mismatch CAS Advisory to populate.