Hi @srdjan29,
We only actively support our Basic ESC. A long time ago (before the Basic ESC had been developed) we used to provide firmware for a collection of other ESCs, but that’s no longer maintained, and I’m unsure if it still works, or which particular ESCs it’s compatible with. This post (from 2016) may be helpful, but beyond that there’s not much we can do to help.
If you’re unable to get firmware flashing working, you may need to contact HobbyKing, or get an alternative ESC that already has a suitable firmware.