Always use an Apple-certified MFi cable. Third-party "charging only" cables lack the data pins required to send the loader files.
Your version of iTunes or your Mac/PC OS doesn't recognize the hardware ID of the device. Step 1: Verify Your Firmware (IPSW) loader for iphone9 3d101ap not found better
Visit IPSW.me and ensure the firmware version you are using has a green checkmark. Apple stops "signing" older versions shortly after a new update. If it's not signed, the loader will fail every time. Always use an Apple-certified MFi cable
Avoid USB hubs or front-panel PC ports. Plug directly into the motherboard (the back of the PC) or directly into the side of the MacBook. Step 3: Enter DFU Mode (The "Deep" Reset) loader for iphone9 3d101ap not found better