She has a GTS 250ie in like new condition. Always garages. Just installed fresh battery. When input the key in, everything lights up like normal, but when pushing starter button, nothing happens. Fresh gas. One owner. No mods at all. Never dropped or or wrecked. Worked fine when we parked it last year, but trying to start it this year and it won't. It's almost like I'm locked out of the ignition. I don't know what to do. Seems like some kind of anti theft or override maybe. Never had this trouble before. I sure hope someone can help me. I don't know what else to do.

Hello. Check that the ignition switch is not off. This is located on the right side. See https://www.manualslib.com/manual/1741647/Vespa-Gts-Supertech-300-Hpe.html?page=70#manual figure 02_14. Sometimes it has happen to me that I inadvertently turn it off and I had experienced the same issue you have.