No screen when connected to hdmi

Hi, everyone. I have a t470: i5-7300u, hd620, I have a problem with the dock or with the hdmi in general. The dock it's a ThinkPad Ultra Dock 40A2, so it should be a simple port replicator. If I turn on the pc and I connect it to the dock or with hdmi display indicates no output but the pc still works on laptop display. If I turn on the pc directly in the dock the sistem "boots" but the screen it's black on the laptop an no signal on the external one, anyway the keyboard makes sounds I can raise volume also luminosity but there is still no output, does anyone know why? My efi it's at: https://github.com/t0mmas0/T470-Hackintosh-OC-BigSur-7300u