Why it doesnt change gears?

Search for Prius forums where owners and diyers share info. Hybrids are different from ice power and requires knowledge of EFI systems, engines, hybrid electronics, interfacing engine and ev mode, etc. Not an easy diy project unless a person is willing to be patient and learn complicated interactions between ice and ev electronics. There may be ev and hybrid forums too, for learning about hybrid control systems. And lastly, subscribing to repair data sites like Alldata.diy or Mitchell Data can give you service manual information or buying info from Toyota.