The loader is only requested when the device is in Recovery Mode or DFU Mode with a specific state. If your device is in:
Fix: Force DFU mode (Hold Power + Home for 10 seconds, then release Power but keep Home for 8 seconds). Loader For Iphone9 3-d101ap Not Found
In ARM‑based iOS devices, a “loader” typically refers to a low‑level bootloader component – either the SecureROM (BootROM), iBoot, or a second‑stage loader like LLB (Low Level Bootloader). When a custom tool (e.g., checkra1n, libirecovery, or a ramdisk loader) fails to find a required binary, it returns a “loader not found” error. The loader is only requested when the device
Many loaders require the device to be in a specific DFU state. If the device is in Standard Recovery Mode or simply powered off, the loader cannot parse the correct d101ap identifier. Fix: Force DFU mode (Hold Power + Home
The loader tool you are using does not have the d101ap profile in its database. Older versions of checkra1n (pre-0.12.2) sometimes failed to recognize the iPhone7,3 variant correctly.