DTE & Fuel Gauge reading empty with full tank

[rosebush]

My DTE and fuel guage keeps reading empty even after half filling the tank. Its like its stuck on Zero and beeps all the time.
Im assuming it has something to do with removing the boot carpet as it started straight after we did this.
This has happened in the past a couple of years ago (Again from removing the carpet) but then just one day fixed itself????
Any ideas please on where to start? Thanks