Works as expect after some edits.
In the Nextion Editor I had to change the 'fuel gap' page name to 'fuelgap' to remove the space. It complied and uploaded to the Nextion successfully. Next, I had to edit the .hmijmap file to replace every 'fuel gap' text to 'fuelgap' by using WordPad. Simhub was able to read the template with the proper telemetry after that.