Homestead Portability

After owning a home in Lake County, Fl for 11 years, we sold and built a smaller home in Marion County. This was 2018.
Filed online for homestead exemption. They could not file Portability online so they sent me an email which went to junk.
Bare in mind we knew nothing about homestead portability so we lost the benefit forever. That's thousands of dollars.
The assessors office has told me since it's past 3 years we're out of luck.
Seriously?