Since I started using XD instead of sketch I have had issues with file sizes when prototyping web designs. To deal with this I wanted to install a plugin called "Image Optimizer". When attempting to install this plugin I just get a loading wheel with no type of progress it just keeps running. I attempted to install other plugins and get the same issue. No errors it just keeps spinning.
We're so sorry to hear about the trouble. Please try renaming the file ExMan.db from this location:
Windows: C:\ProgramData\Adobe\Extension Manager CC\Configuration\DB\
macOS : /Library/Application Support/Adobe/Extension Manager CC/Configuration/DB/
To rename the file, you can simply add +old after Exman, and once you have renamed the file reboot your computer and then try re-installing the plugins and let us know how it goes.
We are sorry to hear you are having trouble installing plugin in XD. In addition to what vertika has said, are you facing trouble installing this specific plugin or all the plugins? What is the XD version of your machine?