I discovered that in CentOS 7.7 my NIC was now defaulting to WOL disabled (in 7.6 it defaulted to "magic packet"). I followed the steps here to enable WOL/magic packet for my NIC with nmcli (nm-connection-editor is the GUI way). At this point I thought my problem was solved but alas, my computer still wouldn't resume from suspend via a WOL magic packet.
In nm-connection-editor I noticed my interface's "Link negotiation" was set to "Ignore". This appeared to be a safe setting, my NIC was correctly negotiating to gig/full. However I decided to see if setting this to auto-negotiate would help, so I ran this command as root (for my "enp3s0" interface):
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nmcli c modify "enp3s0" 802-3-ethernet.auto-negotiate yes
One bit of additional info. After following the ArchWiki steps (and rebooting) running ethtool (as root) should show that your NIC is configured for "Wake-on: g" (MagicPacket). For example if your interface name is "enp3s0" your command and output would look like this:
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# ethtool enp3s0 |grep Wake
Supports Wake-on: pumbg
Wake-on: g