Once I know this, I can help you find the right VTX table or tell you how to set it up. How to configure VTX tables for drone? - Facebook
Without a correct VTX table, you cannot change your video channel or power output via your radio (OSD/stick commands). If the VTX table is wrong, it may revert to default settings (often 25mW) every time you plug in your battery. How to Configure VTX Tables (Betaflight) vtx-tables
Newer VTXs use SmartAudio 2.1+ (power in dB), while older ones use 2.0 (power in 0-3 values). Once I know this, I can help you