Hi…,
Welcome.
Have just loaded Cessna 172 (G1000) Navigraph at EGTB Rwy 24 without error.
Try closing MSFS, then deleting your content.xml file - the location of this file depends on your sim-version (Steam/Marketplace) - you will find the correct location here .
Content.xml will be recreated when you restart MSFS.
Cheers
Ian