Netgear EX6250v2 - reverting back to OEM firmware


I have installed OpenWRT (23.05.2 and snapshot) on a NetGear EX6250v2 to test it.
The issue is that now I want to return to stock but I can't.
I have followed all the tutorials to do it with nmrpflash and TFTP, but there is no way.
Neither system is working for me.

I have LUCI access to the equipment without problems.

Is there a way to go back to stock firmware?