Okay, so this is strange. Are you sure you waited long enough? Rebooting the Omnia is something I expect to „just work“…
Turris MOX has some reboot problems that are beeing investigated by Turris team at the moment but the omnia should reboot just fine.
Maybe you could try to reflash your router with latest firmware, while resetting it to factory settings always goes back to the software version the router was shipped with, this brings you to latest firmware. See section „Re-flash router“ here: https://docs.turris.cz/hw/omnia/rescue_modes/
If this doesn‘t help so that your omnia reboots at least it may be some hardware failure, so it might be helpful to contact support then… (See link „Getting help“ above)