I've used Krita 2.9 for a while without any problems, until I tried to update it to the newer version. First, I've run the installer (3.0 x64) without uninstalling the old version; IIRC, it's supposed to remove the old version and install the new one. After the installation routine ended without error messages, I still had Krita 2.9. So I uninstalled Krita with the windows system control (or whatever that's called in english), and tried installing Krita 3.0. Again, no error messages, but there was no Krita on my system. No program folder, no shortcuts, nothing (it's not hidden or marked as a system file). I tried again, and the installer found a previous installation of Krita 3.0, and also the program folder where it was supposed to be. I reinstalled it with the same results. I've tried installing as administrator, with firewall and antivirus software turned off, and various versions of Krita - they all detect the previously "installed" version of Krita and I can see the program folder in the installer, but not in the windows explorer. I can install other windows programs without problems. The portable version of Krita kind of works though the pressure sensitivity doesn't (Huion WH1409).
Do you have any suggestions how to get Krita installed, or how to get the tablet to work with the portable version? It worked with the old installation just fine.

There is no difference in code between krita installed through the installer or not; so it won't make a difference for your Huion tablet.

I don't know what's up with the behavour of the installer on your system, but when I tried the 3.0.1.1 installer on my Win8 test laptop that had 2.9 installed, it correctly uninstalled 2.9 and correctly installed 3.0.1.1.

Like boud already said, installing Krita using the installer wouldn't make any difference for your tablet. But I am very interested in your case regarding the installer failing to install Krita (iirc that never happened to anyone else.) Which version exactly were you trying to install?

Every version that can be found on the download page now. IIRC, the first one I tried was 3.0.1.1 x64.
Oh, and I found a portable version that doesn't have the Huion driver issue, it's this one: http://files.kde.org/krita/3/windows/kr ... 0f-x64.zip

Have you tried rebooting Windows?
Which Windows 10 version are you using? Are you on the version 1607 update?

(I am still thinking what else I should ask.)

Rebooting doesnt help. And yes, it's 1607