This is the error message I run into:
An error occurred during the signature verification. The repository is not updated and the previous index files will be used.
GPG error: https://apt.releases.hashicorp.com focal
InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY AA16FCBCA621E701.
Then I ran this:
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys AA16FCBCA621E701
sudo apt-key list
Just to make sure the key has been imported and it has. But I still keep getting the same error message when I run sudo apt-get update