Today, I downloaded Blender 2.82 and attempted to install an add-on that would allow me to export models in a format compatible with the program MikuMikuDance (MMD for short). After doing my research, I attempted to install the add-on while all the files were in a ZIP folder. However, no matter what I try - changing the add-on directory in the Preferences, getting rid of excess dots in file names - the add-on won't show up even though a message indicates it was successfully installed. I've tried looking at other questions regarding similar issues, but nothing seems to help, and I'm at the end of my rope here.
(I don't have the reputation to comment this: Powroupi's latest version of Blender MMD Tools works through version 2.90 (my version). Download it here.)
As mentioned by Kisracora, the plugin needs to be unzipped before the mmd_tools folder can be inserted into the addons folder. (If you're on Windows, you can simply enter the zip folder without unzipping and click-drag the mmd_tools folder in.) If doing that and enabling the plugin in Blender DOESN'T get it to show up, you may want to try rightclick > Properties > Unblock the zip (checkbox near the bottom of the Properties window).
MMD Tools is confirmed to work in the latest version of Blender, so this is not a version issue. However, make sure to double check you are downloading the 2.8+ version of MMD tools, and not a version for 2.79 and below.
Did you make sure to unzip the file before attempting to install the add-on? MMD Tools contains multiple plug-ins, so you may not be able to use Blender's built-in "Install" button.
Unzip the downloaded folder titled "blender_mmd_tools-dev_test" Inside the unzipped folder, there should be a folder titled "mmd_tools." We are going to manually put this in the add-ons folder for our Blender Program. The image below shows the file path for my add-ons folder.
Yours will possibly be the same, but it may be different. If you cannot find it, go to "This PC" and search for "Blender Foundation" to find the folders.
Drag the folder "mmd_tools" into your "addons" folder.
Return to Blender. Go to Edit > Preferences > Add-ons and search for "mmd"
MMD tools should be in the list. If it is not, hit refresh and make sure that "Enabled Add-ons Only" is not checked.