One of the guy's with a bigger helmet size than mine will no doubt jump in with more ideas soon, but a quick search and I yielded one possible thing to check for you to consider, taken from an old post by member *twowheels* (twowheels is an active member here and might jump in with some other input).
"If you remove the tank, on the underside, in the middle is the fuel level sensor. I would check the connector first."
That being said, if you have not had the gas tank off yet on your own, we can help you with some tips on doing that. If you go at it blind, many have dropped their tanks, broken the stiff, ridged plastic fuel line, or worse, broken the fuel pump (EXPENSIVE TOO), so ask for help before going down that road. There is a clip to be manipulated on the fuel line that is a little odd to deal with your first time 'round.
Plus, while you are in there and possibly have the tank off, this would be a dandy time to pull the lid on your airbox and check/service your airfilter (another procedure you might want help with before commencing). If the bike has been sitting awhile, it would be unfortunate to find a mouse-nest or other obstructions in the airbox, plus if the previous rider has left us
, you may not have any way to know the last time anyone has serviced the air filter.
PS: the air-filter is re-usable if it's not damaged... and expensive, don't throw the old one away!
All the best,