GasIt dashboard meter

Hi. I've got a 2021 Broadway which I purchased second hand a few weeks ago.  Haven't had the need to use much gas but ever since I've owned it the dashboard display has shown a full showing of green lights.  Used the van yesterday, first time for a few weeks and most of the time the display doesn't illuminate but when it does, it just has a single red light.  
Sounds to me either like I have a bit of a leak or the dashboard display isn't working.
Did use some gas for cooking last night, so there is at least something in the system.
Is there an easy way of checking if the tank is full or close to empty?

As it is gas I want to be careful and wonder if I can find a local GasIt  dealer whether they will be able to test it (and perhaps even cover it under warranty (hopeful perhaps!).

Any help very welcome.  Thanks!

There is a dial on the tank under the van, you will need to remove the cover to access it, not for every day use but will let you know if there is still gas on board. If you use search function above you will find lots of info about how unreliable the dash meter is.

There's also a YouTube video on how to synchronise the dash gauge to the tank gauge.

You might care to read this, which is relevant:
https://www.autosleeper-ownersforum.com/t33531-guide-to-lpg-cylinder-contents

Cymro

Using gas gauge is a bit of a learning curve .

Ready to go wrote:.. Haven't had the need to use much gas but ever since I've owned it the dashboard display has shown a full showing of green lights.  Used the van yesterday, first time for a few weeks and most of the time the display doesn't illuminate but when it does, it just has a single red light.  
Sounds to me either like I have a bit of a leak or the dashboard display isn't working.
.....
As it is gas I want to be careful and wonder if I can find a local GasIt  dealer whether they will be able to test it (and perhaps even cover it under warranty (hopeful perhaps!).

Any help very welcome.  Thanks!

I believe the annual habitation service should test for gas leaks but I wonder if the fridge was inadvertently running on gas whilst the van was out of use.  I normally keep my fridge's gas supply turned off so this can't happen but once I un-expectantly ran out of gas a few weeks after a habitation service when the fridge must have been tested on gas as the tap was on and I may have thought the fridge was off when it wasn't.

Thanks everyone for your helpful comments. 
I tried to take off the cover this morning but it seemed very fiddly and a squeeze.  So...I popped along to a local GasIt garage where the owner was very helpful and showed me how to get the cover off.  To be honest, he struggled with it for a good 5 minutes and then it took even longer to put it back on afterwards.  Transpires I am almost out of gas so my next journey is to a garage to fill up. 
He did say that they've fitted separate dashboard switches for a number of owners, avoiding the need to struggle under the vehicle when about to board a ferry.
Once I get the gas in I'll need to monitor it to ensure there is no underlying leak.
Thanks again everyone!

There's no need for dashboard switch to cut off gas for ferry. In your handbook you'll find AS statement that turning off at the manifold is all you need to do.

I've installed Mopeka bluetooth sensors to both fresh water and gas tanks so I know exactly what levels are. So much more confidence on the levels now