Visual studio signing failed (signtool.exe error)

I'm seeing the same problem. Signtool does not display any error dialogs but the error code returned is -1073741502 (0xC0000142), STATUS_DLL_INIT_FAILED.

The problem could be related to update KB4535996. I uninstalled the update when I saw the problem and signtool worked normally. The problem returned when I reinstalled the update.

Signtool works if I move the manifest file out of the directory, just like you saw. But I also noticed that signtool works when I move the manifest back into the directory.

Instead of renaming signtool.exe, I found that renaming/removing signtool.exe.manifest allows signtool to run while also still allowing Visual Studio to run it.

I do not know why this is happening or what the side effects of removing the manifest are, but it's enough for my project to build again.

For reference, I encountered this issue after doing a clean VS2019 install in a clean Windows 10 1909 VM (but fully updated shortly after).