Finally the (schannel) issue has been resolved, the main cause of this and other similar issues related to SSL/TLS errors is incorrect security settings in Windows Registry located in HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL. The easiest way to correct SSL/TLS settings is IIS Crypto utility disabling all obsolete protocols, ciphers and leave TLS 1.2, Triple DES, AES ciphers along with SHA hashes only. After changes and computer reboot the error SEC_E_ILLEGAL_MESSAGE (0x80090326) was gone.

Most probably some 3-rd party service or app changed security settings

Unfortunately, there is nothing we can do to fix security settings on your PC. I am sorry.

If you are able to manually write to C:\Program Files\Notepad++\, you might be able to bypass the installer. For writing to that folder, you might have to run Windows Explorer as Admin… or when you paste into that folder, Explorer might ask you for Admin permission). So can download the portable 64-bit NPP v8.1.2 zipfile from the official downloads page and open up the zipfile; then manually copy the executable and the associated config files and plugin/updater DLLs from the zipfile into the appropriate location on the problematic computer (C:\Program Files\Notepad++\ and subfolders).

The first installed Notepad++ was v8.1.1 then an attempt to update manually through the ?-menu instantly gives that pop-up error message. Elevate permission by default is admin, UAC is off and all apps automatically start under admin privileges.

In comparison, v8.1.2 is installed on other 2 computers under Win7 and 10, absolutely no problems to update manually through ?-menu.

Given the “initializesecuritycontext”, I am thinking that Notepad++ is having a hard time asking the OS for the elevated privileges needed to do the update.

Also, if your debug info is correct and you already have v8.1.2 installed, why are you still trying to update? That’s already the newest-released version … and in fact the auto-updater is still looking for v8.1.1, so it shouldn’t even try to install anything.

Questions:

• Are you really trying to update starting at v8.1.2? Or did you really start the process from an earlier version of Notepad++ (and if so, which version did you start from)?
• Did you use ?-menu Update Notepad++ ? Or did you manually download the v8.1.2 installer and run it?
  • If running from Update Notepad++ menu entry, did it ask you to elevate permission? Or were you already running Notepad++ in Admin Mode when you launched Update Notepad++?
  • If running the downloaded installer .exe, did you run it normally or did you use “run as administrator” to give it elevated privileges for installation?
• Or are you saying that you’ve already updated to v8.1.2, but when you try to run after completing the installation, it gives you that error?

Using a search engine on your error message shows that other people have similar error messages in many other applications, and at least one page showed that the error happened with Win7 but not with Win10 when trying to access a website via HTTPS from inside the application. That makes me wonder if the developer changed something in gup.exe or updated libcurl.dll to a version that isn’t compatible with Win7 anymore… I don’t have any Win7 machines to test on, unfortunately. If no one else has been able to help you further, maybe I’ll see if I can find my Win7 virtual machine later this week or this weekend, and see if I can replicate the problem.

In the mean time, please supply the answers to the questions I’ve asked, and anything else that will help us replicate the exact process you followed that caused the error.