Unable to use Plesk login command or install/update extensions after interrupted Plesk upgrade: error while loading shared libraries

Symptoms

• plesk login command fails with the following error:

  # plesk login
  /usr/bin/sw-engine: error while loading shared libraries: libaps.so.1: cannot open shared object file: No such file or directory
  exit status 127

• Updating or installing new extensions get stuck in the Plesk UI forever.

Cause

An interrupted Plesk upgrade, which causes Plesk and system packages to be not fully configured.

Resolution

For Debian/Ubuntu-based systems:

1. Connect to the server via SSH

2. Configure all interrupted packages on the system:

   # dpkg --configure -a

3. Continue the Plesk upgrade:

   # plesk installer

For RHEL-based systems (CentOS/AlmaLinux/RHEL):

1. Connect to the server via SSH

2. Identify the interrupted transaction:

   # dnf history list

   Note: look for the most recent transaction with a Failure return code, then check its details:

   # dnf history info <transaction ID>

3. Have Plesk Installer complete the components that were left unconfigured:

   # plesk installer update --repatch

   Note: this downloads and reconciles a large set of packages and can take a long time. Let it run to completion, do not interrupt it, that can leave the system in a worse mixed-version state than before.

If the pre-upgrade check afterwards reports duplicated packages (Your package system contains duplicated packages, which can lead to broken Plesk update), resolve those before continuing. See How to resolve duplicated packages during a Plesk update on CentOS/RHEL for the exact steps.

4. Continue the Plesk upgrade:

   # plesk installer update

Warning: Do not use dnf distro-sync to try to resolve this. Depending on which Plesk repository build is currently active in /etc/yum.repos.d/plesk.repo, distro-sync can propose downgrading or removing core Plesk components (for example mod_passenger, mod_security, or a PHP interpreter version), which takes hosted websites and mailboxes offline. Resolve this only through plesk installer / dnf history / package-cleanup, not raw package-manager sync commands.