The error indicates that you had already installed the plugin. When you upgraded your web site, did you keep your previous \App_Data\InstalledPlugins.txt ? That's where the record of what plugins are installed is kept.
The error indicates that you had already installed the plugin. When you upgraded your web site, did you keep your previous \App_Data\InstalledPlugins.txt ? That's where the record of what plugins are installed is kept.
I added the two files back, after uploading it, which was suggested in the upgrade notes.
I'll see if I can delete that line from that text file to correct it --- THANKS!