Officially, the 4th Generation Intel processors supported by this board do not meet the Windows 11 system requirements. However, it runs Windows 10 exceptionally well.

What (CPU, RAM, GPU) you are trying to install? Are you migrating the motherboard into a new computer case ? Are you encountering a specific error or boot issue ?

Acer H81H3-AM V1.0 Motherboard Manual, Drivers, and BIOS Update Guide

Note: While some users seek "ECS H81H3" manuals, the Acer H81H3-M7 user manual

If your computer fails to boot after making changes to settings or hardware components, execute a hardware reset: H81H3-I Manual and Specifications | PDF | Computer Science