I’ve just purchased the theme and currently have the same issue with the JPlugin update issue.
It won’t activate the plugin as it says it needs updating. When you click update, it reloads the page but does nothing.
I have followed the advice above, de activated plugins and theme.
Deleted them and re installed.
Still getting the same error message.
Can you please advise where I can download the zip file for version 1.1.1. for JPlugin?