Can't change register value on Flash memory

I use EK-TM4C129XL

I'm trying to change the value in flash register using API function:

FlashProgram(&_dataBuffer, FLASH_ADDRESS, sizeof(_dataBuffer));

and receive return value -1.

FlashErase for this address returns 0, but doesn't change value.

I checked the protection setting for this address with function  FlashProtectGet and it is  FlashReadWrite.

Resetting the board doesn't help.

How can I resolve the problem?

Thanks