You really should obtain an owner's handbook - and read it.
Some 2-stroke engines used an oil injection system which is or was considered superior to mixing oil and petrol which is fine and dandy if it works ok and if the rider can remember to top up the oil container - if it works and is topped up there is no need to mix oil with the fuel.
Some oil injection systems proved unreliable and some riders proved unreliable and both scenarios result in expensive engine damage.
Many more experienced riders opt to forget the oil container and play safe by mixing oil with the fuel while others continue to use the oil injection system, insisting it is adjusted so there is a hint of blue smoke from the exhaust proving it is working.
There should be a mechanical release fitted. Insert your ignition key. Push the key away from you, further into the key hole. While pushing the key turn it counter clockwise, the wrong way. The seat should 'pop' open.
You have a bad battery or disconnected something . Major disconnect. I own piaggio equipment many of.. the clicking is also a known issue with start relay being way underated it's 50A and should be 100 min. There's a recall or upfit look son A1 site out of Texas. . Clicking is start relay . Not getting enough juice . Battery is low . . Or no good usually. Get something in their besides a 12 Y battery try a 15 ETX DEKA
Check your fuses first then check rectifiers or regulator they are same thing and you can by new rectifiers really quit cheap do not get sucked in and pay 100 dollars or more when you get one from 10 dollars to 20 dollars on ebay a bike shop will say new need a special one which will cost alot look on utube how to check your rectifier and that should fix it if thats not the problem it is your stator but they usually last for ever