To resolve this issue, use a text editor as the root user to edit the /etc/pf.anchors/com.apple file. Locate the following line near the end of the file:
load anchor "400.AdaptiveFirewall/" from "/Applications/Server.app/Contents/ServerRoot/private/etc/pf.anchors/400.AdaptiveFirewall"
Edit the line to remove the forward slash character "/" after the first "400.AdaptiveFirewall". After editing the line, it should appear like this:
load anchor "400.AdaptiveFirewall" from "/Applications/Server.app/Contents/ServerRoot/private/etc/pf.anchors/400.AdaptiveFirewall"
Save changes to the file, then use the pfctl command to reload rules and enable the packet filter:
sudo pfctl -f /etc/pf.conf
sudo pfctl -e
Alternative non-interactive procedure
As an alternative to the procedure described above, system administrators may use the following command to edit the file non-interactively:
sudo ruby -an -i.bak -e 'puts $_ =~ /^(load anchor "400.AdaptiveFirewall)\/(".*)/ ? $1<<$2 : $_' /etc/pf.anchors/com.apple