If you're looking for the firmware link, I recommend checking the manufacturer's website or online forums, such as XDA Developers or Android TV box communities. You can also try searching for the firmware on websites like Firmware-StockRom or AndroidFileHost.
Do not download anything until you complete this step. You must open the plastic case of your TX9 Pro (the warranty is already void if you are here).
Go to > Device Preferences (or About ) > System Update . Click Check for Updates while connected to Wi-Fi. Manual USB Flashing : Download the .bin , .img , or .trx firmware file.