Irtsgbr

Today, running apt in all my machines gives this error with the Google PPA (for google-chrome):

me@mymachine:~$ sudo apt clean && sudo apt update && sudo apt full-upgrade -y && sudo apt autoremove -y && sudo apt autoclean -y && sudo snap refresh 
[sudo] password for me: 
Ign:1 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:2 http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu bionic InRelease
Hit:3 http://dl.google.com/linux/chrome/deb stable Release 
Hit:4 http://archive.ubuntu.com/ubuntu bionic InRelease 
Get:5 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88,7 kB]
Get:6 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74,6 kB]
Err:7 http://dl.google.com/linux/chrome/deb stable Release.gpg
 The following signatures were invalid: EXPKEYSIG 1397BC53640DB551 Google Inc. (Linux Packages Signing Authority) <linux-packages-keymaster@google.com>
Get:8 http://archive.ubuntu.com/ubuntu bionic-security InRelease [88,7 kB]
Get:9 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [574 kB]
Get:10 http://archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages [488 kB]
Get:11 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 DEP-11 Metadata [278 kB]
Get:12 http://archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 48x48 Icons [66,7 kB]
Get:13 http://archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 64x64 Icons [123 kB]
Get:14 http://archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [756 kB]
Get:15 http://archive.ubuntu.com/ubuntu bionic-updates/universe i386 Packages [745 kB]
Get:16 http://archive.ubuntu.com/ubuntu bionic-updates/universe Translation-en [201 kB]
Get:17 http://archive.ubuntu.com/ubuntu bionic-updates/universe amd64 DEP-11 Metadata [209 kB]
Get:18 http://archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 48x48 Icons [191 kB]
Get:19 http://archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 64x64 Icons [360 kB]
Get:20 http://archive.ubuntu.com/ubuntu bionic-updates/multiverse amd64 DEP-11 Metadata [2.468 B]
Get:21 http://archive.ubuntu.com/ubuntu bionic-backports/universe amd64 DEP-11 Metadata [7.352 B]
Get:22 http://archive.ubuntu.com/ubuntu bionic-security/main amd64 Packages [296 kB]
Get:23 http://archive.ubuntu.com/ubuntu bionic-security/main i386 Packages [216 kB]
Get:24 http://archive.ubuntu.com/ubuntu bionic-security/main amd64 DEP-11 Metadata [204 B]
Get:25 http://archive.ubuntu.com/ubuntu bionic-security/universe i386 Packages [127 kB]
Get:26 http://archive.ubuntu.com/ubuntu bionic-security/universe amd64 Packages [131 kB]
Get:27 http://archive.ubuntu.com/ubuntu bionic-security/universe Translation-en [74,2 kB]
Get:28 http://archive.ubuntu.com/ubuntu bionic-security/universe amd64 DEP-11 Metadata [20,8 kB]
Get:29 http://archive.ubuntu.com/ubuntu bionic-security/universe DEP-11 48x48 Icons [12,2 kB]
Get:30 http://archive.ubuntu.com/ubuntu bionic-security/universe DEP-11 64x64 Icons [50,4 kB]
Get:31 http://archive.ubuntu.com/ubuntu bionic-security/multiverse amd64 DEP-11 Metadata [2.464 B]
Fetched 5.183 kB in 2s (2.131 kB/s) 
Reading package lists... Done
Building dependency tree 
Reading state information... Done
All packages are up to date.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://dl.google.com/linux/chrome/deb stable Release: The following signatures were invalid: EXPKEYSIG 1397BC53640DB551 Google Inc. (Linux Packages Signing Authority) <linux-packages-keymaster@google.com>
W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg The following signatures were invalid: EXPKEYSIG 1397BC53640DB551 Google Inc. (Linux Packages Signing Authority) <linux-packages-keymaster@google.com>
W: Some index files failed to download. They have been ignored, or old ones used instead.
Reading package lists... Done
Building dependency tree 
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Reading package lists... Done
Building dependency tree 
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Reading package lists... Done
Building dependency tree 
Reading state information... Done
All snaps up to date.

Already tried importing GPG key again with:

wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -

Source: Google Linux Software Repositories

This is the protection you are getting from these checks. You don't want to update your software right now while something is messed up on Google's end. Wait until they fix it. Don't try to override by reinstalling keys until some official word comes out that a new key is the solution.

Apparently Google did not extend the validity of the signing cert...
it was due to end today and so it did.
https://pgp.surfnet.nl/pks/lookup?op=vindex&fingerprint=on&search=0x7721F63BD38B4796

maybe Google will change it, today or so… then the update of the cert should work fine and everything should go back to normal.

Looks like Google's signing keys expired. Be patient and wait for them to fix them (which may or may not require re-adding the key after they fixed it).

If you have that in all of your machines, have you thinked that the problem might be invalid key signing on google side? Maybe wait a day and see if the problem is gone. For now you have done everything you could, on your side.