Update problem

[Richard Mockler]

While attempting my update this evening I ran into this problem. Following instructions, I have include the log.
Richard Mockler

============ Log ===========

Hit:1 http://apt.keepsolid.com/ubuntu bionic InRelease
Ign:2 http://cdn.dyn.com/dynupdater/debian stable/ InRelease
Get:3 http://cdn.dyn.com/dynupdater/debian stable/ Release [1,481 B]
Hit:4 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Get:5 http://cdn.dyn.com/dynupdater/debian stable/ Release.gpg [287 B]
Get:6 http://us.archive.ubuntu.com/ubuntu bionic-security InRelease [83.2 kB]
Hit:7 https://repo.skype.com/deb stable InRelease
Get:8 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Ign:5 http://cdn.dyn.com/dynupdater/debian stable/ Release.gpg
Ign:9 https://dl.bintray.com/hawkeye116477/waterfox-deb release InRelease
Get:10 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Get:11 https://dl.bintray.com/hawkeye116477/waterfox-deb release Release [1,842 B]
Get:12 http://us.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [290 kB]
Hit:14 http://repo.linuxliteos.com/linuxlite diamond InRelease
Get:15 http://us.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages [262 kB]
Get:16 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe i386 Packages [161 kB]
Get:17 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [161 kB]
Get:18 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe Translation-en [73.6 kB]
Hit:19 http://ppa.launchpad.net/danielrichter2007/grub-customizer/ubuntu bionic InRelease
Hit:20 http://archive.canonical.com/ubuntu bionic InRelease
Hit:21 http://ppa.launchpad.net/otto-kesselgulasch/gimp/ubuntu bionic InRelease
Hit:22 http://ppa.launchpad.net/teejee2008/ppa/ubuntu bionic InRelease
Reading package lists...
W: GPG error: http://cdn.dyn.com/dynupdater/debian stable/ Release: The following signatures were invalid: CE739DA31CC6A6AF2DABB450C0943F422A34BCA6
E: The repository 'http://cdn.dyn.com/dynupdater/debian stable/ Release' is not signed.