I have 2 different red hat dhcp servers.
I new rhel 8.2 and an older 6.10 backup that needs to be replaced this summer.

Anyways, I need to block a couple MACs from getting IPs.

I can put in 1 entry, but then the second entry causes dhcpd to not fail restarting.

I put in host name {
hardware ethernet (mac address);
deny booting;
}

If I put in 1 entry like this, dhcpd restarts fine.
If I add a second entry, it fails reboot.
It points to an error on the last line, which ends with }

This happens on both dhcp servers.
Any particular reason why?

try the -t option which checks syntax.

I may have it figured out. I didn't number the host name. I think that might be it.

Worse comes to worse. Set static arp for those addresses and don't forget it.