Have you tried clearing your browser's cache ?
You might also need to login to the PluginStore separately, it's on a separate server...
[top-right corner button - same user/pwd as here] ?
You obviously logged into this section - because you posted this !
Can you open this link ?
https://sketchucation.com/pluginstore?pln=ToolsOnSurface
You also need his Lib:
https://sketchucation.com/pluginstore?pln=LibFredo6