Connect the MacBook Neo to its power adapter and disconnect all accessories.
Make sure the adapter and charging cable are firmly connected and, if possible, verify that the Mac is receiving power.
Apple recommends checking the power connection and removing accessories when a Mac doesn't turn on. Apple: If your Mac doesn't turn on
Press and continue holding the power button. If Loading startup options or the Options gear appears, select Options >> Continue to enter macOS Recovery.
From Recovery, you can use Disk Utility to check the startup disk and, if necessary, reinstall macOS without first erasing the disk. Apple: How to start up from macOS Recovery Apple: How to reinstall macOS
If an Apple logo or progress bar appears, allow the startup process to continue.
Because the Mac was in the middle of a macOS installation, avoid interrupting it again unless there is a specific reason to do so. Apple: If your Mac starts up to an Apple logo or progress bar
If the Mac remains completely unresponsive and Recovery cannot be accessed, Apple documents a firmware revive for certain startup and macOS installation problems on compatible Macs.
A revive does not erase the Mac; a restore does. Apple: How to revive or restore Mac firmware
The important next detail is what happens when you hold the power button: Startup Options, an Apple logo or progress bar, a blank screen, or no response at all.
That will determine the appropriate next step.