My new Samsung 8K tv keeps losing source connection to directtv thru my new receiver

This could be an HDMI handshake issue. What is the receiver model? Have you tried a different HDMI cord/HDMI input?

What model box?

Verify HDMI cable is free of debris and secure on both ends.

Coax is finger tight.

If TV has HDMI-CEC, turn it off.

Make sure DirecTV box is not plugged into a 'smart' power strip.

Try another HDMI cable and/or input on the TV.

Red button reset DirecTV box (if Mini Genie reset the main Genie first)

Update firmware/software on the TV.

If after that it is still happening, see if you can swap with another box. Check if problem follows box or stays with just that TV.

HR54-200

Have tried re-booting everything; we have new cables. Had Geek squad out and thought they had fixed it, now back to same thing.

Did you try a different HDMI port? What happens when you try to plug in another device to the same port as the DIRECTV receiver? ( I.e. computer, streaming device)

Did not try that. Thanks; I will let you know.