How do I solve this sudo apt update error?

Err:9 http://download.opensuse.org/repositories/home:/pzz/xUbuntu_20.04  InRelease

  The following signatures were invalid: EXPKEYSIG 23E07629B9E3C9E4 home:pzz OBS Project <home:[email protected]>

Fetched 2,441 B in 3s (819 B/s)

Reading package lists... Done

Building dependency tree       

Reading state information... Done

19 packages can be upgraded. Run 'apt list --upgradable' to see them.

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://download.opensuse.org/repositories/home:/pzz/xUbuntu_20.04  InRelease: The following signatures were invalid: EXPKEYSIG 23E07629B9E3C9E4 home:pzz OBS Project <home:[email protected]>

W: Failed to fetch http://download.opensuse.org/repositories/home:/pzz/xUbuntu_20.04/InRelease  The following signatures were invalid: EXPKEYSIG 23E07629B9E3C9E4 home:pzz OBS Project <home:[email protected]>

W: Some index files failed to download. They have been ignored, or old ones used instead.

I have tried solutions from post How do I fix the GPG error "NO_PUBKEY"? but they did not work:

$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 23E07629B9E3C9E4

[sudo] password for master: 

Executing: /tmp/apt-key-gpghome.QYq1pmnpyE/gpg.1.sh --keyserver keyserver.ubuntu.com --recv-keys 23E07629B9E3C9E4

gpg: keyserver receive failed: Server indicated a failure

$ gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv ^C

$ 23E07629B9E3C9E4^C

$ gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv 23E07629B9E3C9E4

gpg: keyserver receive failed: No data