SSH key randomly stopped working -- user@host.com: Permission denied (publickey).

```
OpenSSH_9.2p1, OpenSSL 3.0.8 7 Feb 2023
debug1: Reading configuration data /home/user/.ssh/config
debug1: /home/user/.ssh/config line 1: Applying options for *
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to host.com [IP.IP.IP.IP] port 22.
debug1: Connection established.
debug1: identity file /home/user/.ssh/id_rsa type -1
debug1: identity file /home/user/.ssh/id_rsa-cert type -1
debug1: identity file /home/user/.ssh/id_ecdsa type -1
debug1: identity file /home/user/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/user/.ssh/id_ecdsa_sk type -1
debug1: identity file /home/user/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /home/user/.ssh/id_ed25519 type -1
debug1: identity file /home/user/.ssh/id_ed25519-cert type -1
debug1: identity file /home/user/.ssh/id_ed25519_sk type -1
debug1: identity file /home/user/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /home/user/.ssh/id_xmss type -1
debug1: identity file /home/user/.ssh/id_xmss-cert type -1
debug1: identity file /home/user/.ssh/id_dsa type -1
debug1: identity file /home/user/.ssh/id_dsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_9.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.4p1 Debian-5+deb11u1
debug1: compat_banner: match: OpenSSH_8.4p1 Debian-5+deb11u1 pat OpenSSH* compat 0x04000000
debug1: Authenticating to host.com:22 as 'user'
debug1: load_hostkeys: fopen /home/user/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: mailto:chacha20-poly1305@openssh.com MAC: compression: none
debug1: kex: client->server cipher: mailto:chacha20-poly1305@openssh.com MAC: compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-ed25519 SHA256:/tC1NzMgwd4Iek+WhI9qRw/TbLXG2ogRVL0QDVUY8fA
debug1: load_hostkeys: fopen /home/user/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: Host 'host.com' is known and matches the ED25519 host key.
debug1: Found key in /home/user/.ssh/known_hosts:1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: get_agent_identities: agent returned 1 keys
debug1: Will attempt key: main SSH key ED25519 SHA256:ILeN0jWD7UB1esK9DNq69Ie+rakdEWKrBDdLWgNAQTs agent
debug1: Will attempt key: /home/user/.ssh/id_rsa
debug1: Will attempt key: /home/user/.ssh/id_ecdsa
debug1: Will attempt key: /home/user/.ssh/id_ecdsa_sk
debug1: Will attempt key: /home/user/.ssh/id_ed25519
debug1: Will attempt key: /home/user/.ssh/id_ed25519_sk
debug1: Will attempt key: /home/user/.ssh/id_xmss
debug1: Will attempt key: /home/user/.ssh/id_dsa
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: main SSH key ED25519 SHA256:ILeN0jWD7UB1esK9DNq69Ie+rakdEWKrBDdLWgNAQTs agent
debug1: Authentications that can continue: publickey
debug1: Trying private key: /home/user/.ssh/id_rsa
debug1: Trying private key: /home/user/.ssh/id_ecdsa
debug1: Trying private key: /home/user/.ssh/id_ecdsa_sk
debug1: Trying private key: /home/user/.ssh/id_ed25519
debug1: Trying private key: /home/user/.ssh/id_ed25519_sk
debug1: Trying private key: /home/user/.ssh/id_xmss
debug1: Trying private key: /home/user/.ssh/id_dsa
debug1: No more authentication methods to try.
mailto:user@host.com: Permission denied (publickey).

```