Unable to update Plesk: The following signatures couldn't be verified because the public key is not available

Symptoms

• Unable to update Plesk or install PHP updates, the process fails with one of the following errors.

• On Debian/Ubuntu, Tools & Settings > Updates shows:

  PLESK_ERROR: Error: Unable to receive update information for the package(s)

• On Debian/Ubuntu, apt update or /var/log/plesk/install/autoinstaller3.log shows:

  CONFIG_TEXT: GPG error: http://autoinstall.plesk.com/PHP82_17 bookworm InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5B6AB2160B50DB96

• On CentOS/RHEL/AlmaLinux/Rocky Linux, dnf update fails the GPG signature check for Plesk packages, for example plesk-php83.

  Note: The repository name and key ID may differ, for example older cases refer to NO_PUBKEY BD11A6AA914BDF7E.

Cause

The Plesk GPG key used to sign the repositories or packages is not installed on the server. This happens when Plesk starts signing packages with a new key (for example 5B6AB2160B50DB96, created in August 2026) that is not yet installed locally, and an older copy of the Plesk key file is used.

Resolution

Warning: Plesk services (for example PHP-FPM) may restart briefly while updates are applied. Create a snapshot or backup of the server before proceeding.

1. Connect to the server via SSH

2. Update Plesk and its components, which also installs the current Plesk signing keys:

   # plesk installer update

3. Verify the repositories.

   For Debian/Ubuntu:

   # apt update

   The PHP repositories (for example PHP82_17 and PHP83_17) should show Hit or Get without NO_PUBKEY warnings.

   For CentOS/RHEL/AlmaLinux/Rocky Linux:

   # rpm -q gpg-pubkey-0b50db96*

4. If the key is still missing, install it manually from the official Plesk URL.

   For CentOS/RHEL/AlmaLinux/Rocky Linux:

   # rpm --import https://autoinstall.plesk.com/plesk.gpg
   # rpm -q gpg-pubkey-0b50db96*

   Then apply the updates in Tools & Settings > Updates.

   For Debian/Ubuntu:

   # curl -sS https://autoinstall.plesk.com/plesk.gpg | gpg --dearmor | tee /etc/apt/trusted.gpg.d/plesk.gpg > /dev/null
   # chmod a+r /etc/apt/trusted.gpg.d/plesk.gpg
   # apt update

Note: Only import keys from the official Plesk URL https://autoinstall.plesk.com/plesk.gpg.