Modern Vespa

With one exception the front fork lock seems to be working ok. It locks the fork when I push the lock button; the light on the dash seems to be working normally. But everytime I push the lock button the horn starts beeping. Usually 2-3 off-on pushes on the button shuts it up but it will not stop beeping when I lock it. What is going wrong? I have not ridden it for several weeks but start the engine and let it warm up even when I do not ride it.

Any advise would be appreciated.

You could be low on hydraulic fluid (normal DOT4 brake fluid) in the reservoir. Take front panels off to inspect.

Almost certainly you have low hydraulic pressure or air in the system.
Take off the front inspection panel.
Remove badge and screw underneath then remove "V" panel by getting a finger in the side edges at the top and run down the edge and it will pop off as it's held on by rubber grommets in a similar way to some bike side panels.
Check the fluid level.
I would guess air in the system if you are leaving it for a couple of weeks.
It's easy to bleed the system.
For safety put it on the stand.
Operate the tilt lock a few times then leave the lock on.
Turn the steering so you can get at the bleed nipples at the top of the shock absorbers on either side.
Then just quickly crack open and close each bleed nipple in turn checking fluid level and/or operate tilt lock between bleeding.
Don't completely bleed it just quickly open/close the nipples.
Just drape a cloth over the calipers/discs as surplus fluid can drop on the brakes.

I will follow up as per your advise.