My macbook won’t turn on or charging

I think is that the MagSafe LED is completely dead, not simply that macOS fails to boot. On an M4 MacBook Pro, that points more toward the machine not reaching the normal power/charging-management state at all, so I’d troubleshoot the power path rather than Finder/macOS.

Since this happened while the Mac was powering an iPhone, I’d first disconnect absolutely everything, including the iPhone, MagSafe and any USB-C devices, then connect only the original MagSafe charger directly to the Mac and watch for any LED response.... if you have a USB-C PD charger, also test that directly on a USB-C port, because MagSafe and USB-C use different physical charging paths and that test can tell you whether this is isolated to MagSafe or the Mac’s broader power-input/PD circuitry.

If neither input produces an LED, charging indication, trackpad haptic response, keyboard activity or any measurable sign of power after several minutes, I’d suspect the system’s power-management/charging controller is stuck or that there is a hardware fault on the power-input/logic-board side rather than a normal battery discharge.

The iPhone itself is unlikely to have somehow drained a healthy M4 battery into a permanently dead state; more plausibly, the connection coincided with a fault or abnormal USB-C/PD power-state transition. At that point, repeated Touch ID holds aren't going to repair the underlying condition, and Apple Diagnostics/service is warranted, especially if both MagSafe and USB-C charging are completely unresponsive.

See this article.

If your Mac doesn't turn on - Apple Support