You have created or updated a query and while trying to add/update it to a dashboard panel you get the following pop-up error:
This might be due to the length of the query you are trying to use to create a new panel. Queries built for dashboards/panels have a limitation of 10,240 characters, if you go above this number the panel will fail to be added to a dashboard with the error "There was a problem adding panel to the dashboard."
You have to optimize your query to use less than 10,240 characters. You can use a tool like www.lettercount.com to count the characters in your query.