Zorin 18.1 Pro - The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 55E9312A15BE5896

[MHC]

I noticed this afternoon that for some reason I had no updates for any apps on my Zorin 18.1 Pro . I also couldn't find any OS upgrades / updates. It said failed to download repository.

I explore the topics on here ( Software App does not find updates ) and ( N: Missing Signed-By in the sources.list(5) after running '$sudo apt-get update' ) and a few others but am none the wiser.

I appear to have the PUBKEY not correctly set, but the keys are exactly correct as per N: Missing Signed-By in the sources.list(5) after running '$sudo apt-get update' - #24 by Ponce-De-Leon <== Note the keys pasted into this post are identical to the keys I have on my Zorin OS.

Please see:

and

Where do I get the correct Public Keys from without using apt-key ? I assume getting the correct keys (although it looks like I have them already) would then complete ability to update .

All help and guidance greatly appreciated!

[Ponce-De-Leon]

Please open the File Manager and in the Pathbar at the Top type /etc/apt and press Enter. Then check if You have a zorin.list File in sources.list.d. If yes, post the Content of it here. Also show what Files are in /etc/apt/sources.list.d

Then go back and check in trusted.gpg.d if there is a zorin-os-premium.gpg File

[MHC]

Zorin.list has :

deb https://packages.zorinos.com/apps noble main

deb https://packages.zorinos.com/premium noble main

And yes, zorin-os-premium.gpg exists.

[MHC]

Ok I've actually somehow resolved the problem.

How:

• On the "Software and Updates" settings box, I found there was duplicates under
  
  

( ^^^ these are not the duplicates; this is just the screen I'm referring to)

• "Other Software" . I unchecked all the elements, and closed/saved the "Software and Updates". It caused the same error re Public Key as had in terminal.
• I then commented out the entire contents of "/etc/apt/sources.list.d/zorin.list"
• I restarted the OS.
• I opened "Software and Updates" and used a HTTPS "download from" that was NOT "Main"; I used a Mirror that uses HTTPS (they seem rarer than HTTP ones according to this interface).

And the updates now work ok. No errors.