The links you pointed to were to the old 2017 pre-Notepad++-7.6 “Plugin Manager” plugin’s plugin-list. (There used to be a plugin which handled installing/uninstalling plugins in Notepad++. In v7.6, that was integrated into the core Notepad++ code, so that Don could make sure that the Plugins Admin always stayed compatible with Notepad++, rather than relying on a third party for such an important feature.) For nearly a decade, https://github.com/notepad-plus-plus/nppPluginList/ has been the home of the official list of plugins that gets shown in Plugins Admin.
More on the disappearance of NppCrypt and its repo can be found in this NppPluginList issue. I won’t re-iterate the details, since you can read them there if you are curiuos. But I will say that it looks like @chcg is going to try to resurrect the plugin from archives of the original source code; but it might take him some time. Until then, I’m not sure that any of the links given have any compiled DLL available. Hopefully, you don’t have any critical data that was encrypted on some other machine, that you need to decrypt with the plugin on this new setup. If you do, let us know… (Actually, if you do: do you also have access to the old machine? If so, you can copy the ...\notepad++\plugins\NppCrypt directory from the installation on that machine, and put it on your new machine.)