AskUbuntu: The following signatures were invalid: EXPKEYSIG 1397BC53640DB551
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Re: AskUbuntu: The following signatures were invalid: EXPKEYSIG 1397BC53640DB551
#2>"Apparently Google did not extend the validity of the signing cert... it was due to end today and so it did."[0]
It happens to all of the "too big to fails".
[0] - https://askubuntu.com/questions/1133199/the-following-signat...