Issue Plesk updates failing: 502 Bad Gateway after installer update + “Unable to receive update information” error

[zihniates]

Server operating system version

Ubuntu 22.04

Plesk version and microupdate number

18.0.71 Web Host Edition

Hello,
I’m having a serious issue updating my Plesk server.
Two updates are available:
-Plesk Obsidian 18.0.72
-92 system packages
However, both update methods fail, but in different ways.
System packages update fails when I click Update All, I get this error:

Error: Unable to receive update information for the package(s)
Nothing updates and the dialog closes.

Plesk version upgrade fails (18.0.72 → installer 502 error)
When I try to install the main Plesk update, the installer first updates itself successfully:
Plesk Installer was updated
…but when the page reloads, the Plesk UI returns:
502 Bad Gateway
After that, the installer cannot continue.

Logs from /var/log/plesk/install/autoinstaller3.log

[2025-11-14 22:22:09.172897] Synchronizing the Debian APT package index files...
[2025-11-14 22:22:09.207443] E: Conflicting values set for option Signed-By regarding source https://autoinstall.plesk.com/PMM_1.1.0/ jammy: /etc/apt/keyrings/plesk-ext-panel-migrator.gpg != /etc/apt/keyrings/plesk-ext-site-import.gpg
E: The list of sources could not be read.
Warning: there are errors in 'apt-get update'


[2025-11-14 22:22:09.241096] E: Conflicting values set for option Signed-By regarding source https://autoinstall.plesk.com/PMM_1.1.0/ jammy: /etc/apt/keyrings/plesk-ext-panel-migrator.gpg != /etc/apt/keyrings/plesk-ext-site-import.gpg
E: The list of sources could not be read.


[2025-11-14 22:22:09.275006] E: Conflicting values set for option Signed-By regarding source https://autoinstall.plesk.com/PMM_1.1.0/ jammy: /etc/apt/keyrings/plesk-ext-panel-migrator.gpg != /etc/apt/keyrings/plesk-ext-site-import.gpg
E: The list of sources could not be read.


[2025-11-14 22:22:09.285247] Error: Not found source for system packages (release 22.04) in APT software sources configuration.

 

[zihniates]

rm -f /etc/apt/keyrings/plesk.gpg
curl -fsSL http://autoinstall.plesk.com/plesk.gpg -o /tmp/plesk.asc
gpg --dearmor < /tmp/plesk.asc > /etc/apt/keyrings/plesk.gpg
chmod 644 /etc/apt/keyrings/plesk.gpg
apt-get update

everything fine.