Problem
When using Explorer and viewing data from a large number of sources (e.g. tests), refreshing the page results in a 404 Page Not Found error.
Resolution
This occurs when too many data sources are selected, so the solution is to reduce the number of selected data sources. Each selected data source is listed as a parameter in the page URL, along with other selected options such as breakdowns and dimensions. If the total length of the page URL becomes greater than 2100 characters, the page will not load when refreshed. This would typically occur when 250+ data sources are selected.
This limitation is by design, as Explorer is not intended for viewing data from hundreds of different sources simultaneously.