Issue Signatures couldn't be verified because the public key is not available

[swemp]

root@friendly-gauss:/home/administrator# plesk sbin pum --update
2026-11-06 17:52:42 INFO: pum is called with arguments: ['--update']
2026-11-06 17:52:42 ERROR: Previous Plesk installer call finished unsuccessfully. PUM will not perform any update operations until Plesk installation is fixed.
2026-11-06 17:52:42 ERROR: Exited with returncode 50.
exit status 50

 

[swemp]

root@friendly-gauss:/home/administrator# plesk sbin pum --update
2026-11-06 17:52:42 INFO: pum is called with arguments: ['--update']
2026-11-06 17:52:42 ERROR: Previous Plesk installer call finished unsuccessfully. PUM will not perform any update operations until Plesk installation is fixed.
2026-11-06 17:52:42 ERROR: Exited with returncode 50.
exit status 50

 

[tessa67]

Please send us output from:

ps aux | grep -E '[a]pt|[d]pkg'

dpkg --audit

tail -n 100 /var/log/plesk/install/autoinstaller3.log

tail -n 100 /var/log/plesk/systemupdatestool.log

Possible Repair:
If a stuck apt or dpkg process is actually found, it must first be terminated in a controlled manner.
Afterwards, the repair procedure documented by Plesk is as follows:

dpkg --configure -a
plesk installer update
plesk sbin pum --update

Do not kill processes blindly: First verify whether they are genuinely stuck and not currently performing an active installation.

Regards
Tessa

 

[swemp]

Warning: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. OpenPGP signature verification failed: Index of /pool/PSA_18.0.81_20048 resolute InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57
Warning: Failed to fetch http://autoinstall.plesk.com/pool/PSA_18.0.81_20048/dists/resolute/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E9299045CE550E57
Warning: Some index files failed to download. They have been ignored, or old ones used instead.

 

[Sebahat.hadzhi]

@swemp , could you please try restoring the key with:

curl -sS http://autoinstall.plesk.com/plesk.gpg | gpg --dearmor >> /etc/apt/keyrings/plesk.gpg

 

[swemp]

@swemp , could you please try restoring the key with:

curl -sS http://autoinstall.plesk.com/plesk.gpg | gpg --dearmor >> /etc/apt/keyrings/plesk.gpg

root@friendly-gauss:/home/administrator# curl -sS http://autoinstall.plesk.com/plesk.gpg | gpg --dearmor >> /etc/apt/keyrings/plesk.gpg
root@friendly-gauss:/home/administrator# apt-get update
Hit:1 Index of /pool/PSA_18.0.81_20048 resolute InRelease
Hit:2 Index of /WATCHDOG_3.3.0 resolute InRelease
Hit:3 Index of /ubuntu resolute InRelease
Hit:5 Index of /ubuntu resolute-security InRelease
Hit:6 Index of /ubuntu resolute-updates InRelease
Hit:11 Index of /ubuntu resolute-backports InRelease
Hit:4 Index of /imunify360/ubuntu/26.04/ resolute InRelease
Hit:8 Index of /alt-common/deb/ubuntu/26.04/stable/ resolute InRelease
Hit:7 Index of /ubuntu/26.04/empty_slot-1/ resolute InRelease
Hit:9 Index of /ubuntu/26.04/empty_slot-2/ resolute InRelease
Hit:10 Index of /ubuntu/26.04/empty_slot-3/ resolute InRelease
Hit:12 Index of /ubuntu/26.04/empty_slot-4/ resolute InRelease
Hit:13 Index of /ubuntu/26.04/empty_slot-5/ resolute InRelease
Hit:14 Index of /ubuntu/26.04/empty_slot-6/ resolute InRelease
Hit:15 Index of /ubuntu/26.04/empty_slot-7/ resolute InRelease
Hit:16 Index of /ubuntu/26.04/empty_slot-8/ resolute InRelease
Hit:17 Index of /ubuntu/26.04/empty_slot-9/ resolute InRelease
Hit:18 Index of /ubuntu/26.04/empty_slot-10/ resolute InRelease
Hit:19 Index of /ubuntu/26.04/empty_slot-11/ resolute InRelease
Hit:20 Index of /ubuntu/26.04/empty_slot-12/ resolute InRelease
Reading package lists... Done
N: Missing Signed-By in the sources.list(5) entry for 'Index of /alt-common/deb/ubuntu/26.04/stable/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-1/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-2/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-3/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-4/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-5/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-6/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-7/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-8/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-9/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-10/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-11/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /ubuntu/26.04/empty_slot-12/'
N: Missing Signed-By in the sources.list(5) entry for 'Index of /imunify360/ubuntu/26.04/'

 

[tessa67]

Hi @swemp

The only thing still open is the PUM error (exit code 50).

Can you check if
plesk sbin pum --update
now runs without it?

If it still fails, run
dpkg --configure -a,

then
plesk installer update,

then
plesk sbin pum --update again.

If it still doesn't work, please post the last lines of /var/log/plesk/install/autoinstaller3.log.

Regards
Tessa