The Nav Invalid message at the top of the Entegra EXP5000 PFD is associated with the autopilot installed. For up-to-date info on this message, please review the DFC90 Pilot Guide, or applicable (other vendor) Pilot Guide. Below is an excerpt from the DFC90 PG:
***UPDATE*** October 2022 If you have updated the IFDs to 10.3, you may notice the 'MSG' notification on the PFD will no longer show when the IFDs have an advisory notification (cyan/blue messages from the IFDs). The change was due to pilot feedback. Cautions and Warnings will still display the yellow 'MSG' notific…