I can't install any addons into Blender I know this question has been asked before, but I can't really find a solution. 
This was happening years ago too I think, so... I'm pretty stuck.
I've even re-installed my entire os since then, but I remember addons working at some point.

The two addons I need are these;
https://github.com/sugiany/blender_mmd_tools
https://github.com/ousttrue/pymeshio

I've tried to install them in a couple different ways - I tried using 'install addon' and using the zip, but nothing.
I tried to put the extracted folders into the addons folder of my Blender installation, still nothing.

When I click on the button to install an addon from user preferences, it just does nothing. It doesn't ever appear in the list, and I can't see any errors. This happens every single time I try to install the addons, just nothing happening.

I tried this with a portable install as well, there was no difference.

I realize I'm probably doing something very wrong like an idiot, but I would appreciate some help. Thank you.
These might be the possible errors:-
1. Check if there is sufficient space in the drive your os is installed.
2. Check if the addon downloaded is of correct windows architecture I.e. 32 bit or 64 bit.
3. Check if the blender version you are using is same as mentioned for the addon.
4. Install a stable blender release instead of nightly build or alpha build. 
5. Check that the python version you are using match the one on which the addon is scripted.
6. Check if the addon is complete and is not missing any command line. 

If it still doesn't work you may have a error or bug report on the respective page.