Is it completely dead or just not reading right? See if your bike will start w/out pulling in the clutch lever. If so, you have a bad or dirty clutch switch.
Here's some late night reading material that came up after some Googling results- after all, this is probably a Triumph thing, not just the Rocket3... https://www.thetriumphforum.com/threads/tiger-1050-fuel-gauge-clutch-switch.17629/...